Improving replayability?

I played this game for almost 100 hours with a trio of friends before we all slowly became bored by the relative monotony of the later stages of the game and, while I appreciate how brilliant the game is at the beginning (the first 50-70 hours were incredibly fun and rewarding), it became a drag around the time the mountains/plains rolled around. I understand also that many will keep playing solely for the building mechanics that so many other games lack, but I personally enjoyed the mix of RPG/survival elements that the game had in the beginning. I also understand that each procedurally-generated world is unique and offers different challenges, but they all boil down to similar challenges and strategies/a grind that end up making subsequent playthroughs after the first rather lackluster. I'm curious what you guys think would help improve the replayability of the game?

Personally, I really enjoyed extended boss fights with friends, and would be curious if the developers would add mini-bosses to the various regions that could be tackled solo or in groups as "raids" like those in games like WOW, or like how Fuling villages can be tackled by a group like a raid. It would also be interesting if "magic" elements, like mage-type abilities, could be added, as those always enhanced other similar games I've played. Finally, having non-hostile NPC's, or even neutral towns/villages akin to RPG's with procedural quests/other activities could really add to the fun of the game.