TL;DR below

~3 years ago I came up with a Techies rework and I've been refining that idea occasionally when I was trying to fall asleep lol. I never had time to make a detailed post about it but since a rework was announced I decided to share my ideas.

Why do Techies need a rework?

Don't read this list (skip to the actual rework) if you're tired of hearing about everything wrong about Techies or already know all about it.
The main goal of the rework is to:

Make the hero more team-oriented. A support hero that mostly just deals a ton of damage, needs farm, often lasthits enemies, needs the team to play around him – doesn't really sound like a well-designed support.
Remove the mechanic that allows Techies to solokill an enemy carry out of nowhere. It's annoying and unfair. It encourages extremely passive playstyle and makes the game unfun to everyone but Techies.
Stop Techies from increasing match duration. He has the longest average game length. Not only he's good at defending his base, but he's also really slow at winning the game. The tower damage from proximity mines doesn't help the fact that he needs a lot of time to set up a fight gets too much gold/XP from kill if his team is dominating – the gold/XP a carry could use to easily finish the game.
Remove some possibly minor but annoying mechanics. Techies is the only hero who can Deny himself. Proximity Mines require you to play with sound on. Sounds are really important in Dota but they are not absolutely essential – Proximity Mines are the only exception. Also, Proximity Mines killing creepwaves makes it too easy to ruin a game for your Offlaner. Not a major complaint but I can't dismiss the fact that some hero designs a lot better at ruining games or being toxic than others.
Preserve some of Techies' unique mechanics, don't stop the hero from being fun to play.
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The Rework

P.S. before you criticize the stats, damage numbers etc read the second to last paragraph at the end

First Spell – Proximity Mines replaced by Remote Mines
The goal is to make Remote Mines more of a traditional nuke. Remote Mines now deal 100/165/230/300 damage and you can't plant more than 2/3/4/5 mines (cooldown remains 8 seconds). So you can stack Remote Mines to prepare a 1500-damage (1125 if we consider magic resistance) trap after lvl 7 but you definitely won't be a solo-killer anymore – it's just not worth it to max out a skill and then plant 5 mines somewhere only to disable the skill you've maxed out.

Remote Mines now also get a 1-second blind (miss chance) – 70/80/90/100% to anyone affected by Remote Mines. This is the change that will enable Techies to be a good and more traditional laner while remaining annoying, fun and unique. You could disrupt the enemy carry's farm by blinding them when they're hitting creeps; or improve your ability to trade with the enemy support by blinding them.

This spell would make you a great support. The 1 second AoE blind could save a teammate by decreasing the physical damage they get. Or if your team is really great at planning, you could lure the enemy into 5 of those mines so you can sequentially apply the blind effect for a total of 5 seconds. Not so great against BKB (like any support ability) but at least a basic dispel would save the enemy only from 1 instance of the blind debuff.

Second Spell – Stasis Trap probably remains the same, more below

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Third Spell – Blast Off! replaced by a new ability – Time Bomb

Techies throw a Sticky Time Bomb at an enemy, ally, or stick it to themselves. The Time Bomb will detonate after 4 seconds or when Techies uses the Detonate ability. Detonating the Time Bomb causes the affected ally to leap in the direction they're facing (like Firesnap Cookie) or if you stick the bomb to an enemy the will leap in the opposite direction.
Leap distance depends on activation time. Minimal distance: 100/200/300/400, Max distance: 350/475/600/825. Time Bomb applies a 1/1.5/2/2.5 second silence to enemies. The silence is applied to the where the bomb was detonated if the bomb was sticked to an ally. It's applied to the leap destination if the bomb was sticked to an enemy. Also deals 50/100/150/200 damage (the same rules apply to the damage area).

This ability makes Techies an even better support. You'll be able to save teammates by making them leap or by making the enemy leap backwards. You could also initiate with this ability (keep in mind that the silence won't be applied in this case). It's also possible to reposition the enemy and throw them into you trap using this ability. I've always thought that Techies was missing an ability similar to Force Staff which would synergize well with their trap-setting abilities (and won't require a 3k gold item). It's a strong ability that you should probably max out and what's best is that it makes you play actively and close to your team.

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Ultimate – Minefield

Techies channels the spell and after a short delay Proximity Mines cover the affected area like monkey king's soldiers in an arena. I don't really want to come up with exact numbers (the damage, AoE, amount of mines etc) because it's really hard to balance the numbers without testing anything but I'll still try… Affects 800/900/1000 AoE, with 8/9/10 Proximity Mines in the field, each dealing 100/150/200 damage and applying a 20/30/40% slow. The mines are not invisible. They deal physical damage but are not activated when a spell-immune enemy steps on them. Doesn't affect buildings. 20/30/40 second duration. The position of mines is slightly randomized.

Minefield allows Techies to remain a hero that is great at controlling a large area and wins teamfights if the enemy is lured into it. However previously Techies spent all of his time setting up the traps which made the hero less of a team player and caused him to stay off the map. Techies is really great at securing a position on the map but it's also literally the only thing he's good at. This rework doesn't take away the area-securing aspect of the hero and it allows Techies to move with their team, choose a position and secure the area withing seconds, just like Support Monkey King, Undying, or Shadow Shaman. The ultimate should be used before a teamfight (while taking an tower/roshan) or during and it can do a lot of damage if the enemy isn't careful enough. However it's not hard to counter the spell – you can always use BKB or clear the path from a long range by autoattacking the mines.
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This is the core idea I had and I really hope you like it. Some spells could be balanced one way or another to make Techies fulfill some role better than the other, which I will describe below. I also have some ideas for Techies' Aghanim's Scepter/Shard. Feel free to skip these (except maybe the Scepter upgrade idea) if you're already happy with the abilities I've described and if you're not planning to comment something like "300 damage is too much so this whole rework is trash".
Aghanim's Scepter idea:

Remote Stasis Traps – Grants Techies a new ability. Remote Stasis Traps work exactly like normal Stasis Traps, except they don't trigger on their own – they should be activated with Focused Detonate ability like Remote Mines. 80 second duration, 18 second cooldown, 600 root radius but can't be placed within 400 range of another Remote Stasis Trap. If this sounds weak, consider that normal Stasis Traps almost always root 1 hero. Remote Stasis Traps allow you to wait before several heroes enter the radius before triggering it, resulting in a mini-Overgrowth.

Shard ideas:

Stasis Traps and (Remote Stasis Traps if you have the Aghanim's Scepter) can be thrown like Remote Mines (same cast range). Decreases activation delay by 0.5 seconds.
Remote Mines now have 2 charges.
Time Bomb reaches its max leap distance within 1 second (instead of 4). Still takes 4 seconds to automatically detonate unless you activate it yourself.

Other variations of the new spells:

Remote mines always apply a 100% blind
Remote mines don't have max 2/3/4/5 max amount. They instead have 16/24/32/40 second duration. You'd still be able to plant 2/3/4/5 mines at best, unless you have Octarine Core or Arcane Rune. I don't like this idea because having an expiration time on Remote mines would cause some Techies players to "babysit" their 5-mine traps so there are always 5 mines there or spend 40 seconds setting up another trap when the old trap expires, thus playing without their team.
Time bomb deals triple damage if the Techies sticked the bomb to themselves (50/100/150/200 damage otherwise). The damage affects the enemies and Techies, so Techies can deny themselves with it.
The leap direction and silence/damage area rules can be simplified. Like silence is applied only at the leap destination, no matter if you applied the bomb to an ally or enemy. Or the leap direction is the same for enemies and allies. Also the spell could be more damage-oriented, or have a slow instead of silence.
Minefield could have a 1 second cast time instead of being a channeling spell. The duration, AoE, amount of mines, whether it affects enemies with BKB or not – all of these factors could be played with when balancing it.

P.S: I came up with all the numbers while I was writing this. Feel free to criticize any concept I described or offer some better-balanced numbers but please don't criticize the whole rework because of some numbers. For example, I'm not committed to the idea that Minefield should have 8 Proximity Mines on lvl 6. Could be more, could be less – it really depends on the other numbers. I think the abilities are conceptually balanced and provide a well-designed hero but neither me, nor Valve can know if the numbers are well-balanced before people play the hero. Also I didn't include most cooldowns, manacosts, casttimes, base stats of the hero etc, so feel free to imagine whatever sounds more balanced to you.

Thank you if you read at least some of it and I hope you like it! I also hope Valve's rework is somewhat similar to this, even though the chances are really low lol.

TL;DR: Q casts Remote Mine (2 max on the map at lvl 1, 5 max on lvl 4), normal damage for a basic nuke, applies blind to trade with enemy sup or disrupt enemy carry's lasthitting. W is the same. E casts time bomb: a firesnap cookie with 4 second delay (you can activate it anytime tho), affects allies and enemies – can save ally, help ally initiate, make enemy leap away (they leap in opposite direction), or make them leap into your remote mines/stasis traps. R casts Minefield – 8/9/10 proximity mines like MK's soldiers, high duration, low damage + slow. good arena-like teamfight skill.