Add : traveling to areas, needing to face xcom style situations (assaulting unknown areas. Ship part could literally be an enterable ship like xcom enemy unknown.) . Fog of war for pawns (effecting raiders too, so they can't magically track your colonists. Would also be cool if small animals were hidden by brush, would make animals useful in hunting) . Deeper history stats (let miners have higher melee damage output, and higher haul skills, military people hardened, but not immune to violence, make history add more than skill stats, add / subtract to effectiveness of other things, add traits, ect.).
Remove : mortars from raiders. This was added pre sappers, to negotiate kill boxes. While assaulting a position is fun, it can be easily waited out, and i would much rather attack a full outpost than a few sandbag covered punks. Also scythers. Too fast, accurate, and damaging per shot. Would honestly prefer a 3 shot burst because high damage single shots kill, while light spammy stuff incaps.
Change: add in a psychological system, where you can shape colony "standards" and change people (slowly, and perhaps with a bit of persuasion) to change. So things aren't set in stone as good or bad, and traits can slowly, and difficultly be added, or taken. I think the rimworld would harden and improve people, and i refuse to believe someone on the verge of death would not try Changing (being disabled in mining / construction, short of being physically crippled, i think if things got bad enough, they would try.) more "life" to pawns, namely self preservation (animals don't steer clear of humans, you can go from squirrel to squirrel attacking, they don't run / hide. Maybe make animals / pawns have small, random activities so they seem more allive, especially animals. Rolling on ground to seem cute, playing with things, ect, animals in particular feel robotic. But even the odd colonist goofing around when unexpected, or singing during work would be fun.