I’ve been brainstorming mod ideas and have a few ideas on the go, but they would be extremely heavily impacted on what the crafting system is currently capable of. Namely, is it at all feasible to create scripted entities such as critters, pets, monsters and even citizens using the crafting system? Even if it required the crafter to then take this entity after crafting to the stockpile who would then be placed and become a rabbit / goblin / person with all the scripts, etc included, with crafted citizens immediately joining your settlement, etc?
While this obviously wouldn’t make much sense in the game as it currently is, it would have a major impact on things such as, for instance, engineers begin able to craft, for example, steampunk style clockwork robots to go with there turrets. These robots would be something that while would not function as a civilian themselves (although an entirely mechanical race could be interesting), would act like soldiers and would patrol your base and fight any enemies it finds, “eating” fuels such as wood, coal, etc, instead of food, not needing sleep, being repaired by engineers and being something you would be much happier to lose in a fight then a level 6 knight.