On a game such as RimWorld, a multiplayer feature is always controversial. Most games don't actually implement this, but I think it would be fun on a game like this. Every player should get their own spawn point randomly on the map (with 3 survivors like usual). Everyone will be able to build up their own colonies separately, or even team up. They can trade and become friends, or become rivals with each other. The objective would be to be the last colony last alive by eliminating all of the other colonies. This would make the game much like an RTS. I believe that this feature would definitely not be easy to implement, and would take some time, but I think it would have a massive impact on the game in a positive way.