First off if someone knows somewhere better than reddit where I can express this idea to the devs please let me know, since I think this is a good idea that will improve exploration in the game and give some end game goals for collectors/explorers.
I think it would be really cool if the devs added in more rare finds in the game kind of like the shopkeeper. As far as I'm aware there's only 1 shopkeeper in each world and they are in a random black forest biome so you could possibly find him on the spawn island, or possibly never find him if you don't search far and wide and get unlucky. So why not have other 1 off things that are rare and worth venturing out into the world for outside of natural game progression?
As of right now, there is still a decent amount of exploration needed in order to find all the stuff you need to progress, but I noticed near end-game there was very little reason for me to explore anymore. I found the shopkeeper on a nearby island from spawn, I found multiple of each biome around the spawn island, more than enough to farm everything craftable for 1 person. So it would be cool if there was more rare stuff to look for.
Some ideas: Maybe a giant castle with unique enemies that can only be found in that 1 castle, maybe a mini-boss that drops a cool axe or sword or something. Maybe an excaliber type sword in a stone you can't pull out until your sword skill reaches X amount (to stop you from getting it too early and just rolling through the game with it) in a random meadow. Maybe a rare village with shamans that spawns in a random swamp that again has some sort of rare drop you can only get from that 1 village.
None of this stuff needs to be needed or necessary for endgame just like the shopkeeper, it's just cool stuff that you can possibly find in a playthrough or go out of your way to find if you're an explorer or collector. And it will help make each playthough even more unique depending on which of these rare things you find and which ones you don't in your playthrough (if you're not actively searching the entire map for them).
I understand that the game still has at least 2 more biomes to get set up with more stuff to explore/fight/discover, but that fits into the natural progression of the game like everything else except the shopkeeper. Once you've found a meadow you've basically seen everything that every meadow biome has to offer. So I think adding a bunch of 1 off rare finds in the game like the shopkeeper would help promote exploration even after beating the game and it would make some playthroughs unique depending on what you find and don't find.
Also this game is amazing btw, I have like 150+ hours in it after only a couple weeks, but the game has so much potential and I think this idea is one small thing that could help improve on a game that's already amazing.