[@ScreenAcne] Personally I would say that if we were to use this "growth bar", that actions like war wouldn't help it grow, but more damage anyone else and let you take over say... half their progress. If you and I were both on the planet notEarth and we both went to war having 10% on the bar each and you won, you would get 5% from me instead of just generating 5% from no where.

Now this means I would have only 5% left which draws me to my next idea of having a minimum limit on the bar that once you drop below a certain point, you're out of the planet and would have to try again from stratch or go somewhere else. Like, if you drop below 8%, you get the boot but your colony starts out with something like 20% ish (just throwing numbers out). If the GM/players are willing, there could also be random events that happens to everyone, picked from a player generated list of events with a dice roller/RNG that could provide buffs or debuffs which players would have to represent in their new posts.

Also like your special rules idea, sounds neat.