Well you cannot use dead planets because the technology to build and enclosed sealed space doesn't exist.... it has not existed ever since submarines were first never invented. and it has not existed ever since space craft were first never invented.
I agree.
lol,
An outpost on a dead world is possible at our current level of technology right now... so it is perfectly understandable that primitive space aged races would not be able to do it.
Sarcasm aside, i will ad a more constructive comment as well and say that you could make 'outposts' possible for dead worlds in the game. These outposts would add mining support to starbases, and a little bit of science output.... since there will always be things to study on foreign worlds dead or alive.
I guess it would function like a starbase, and you can add more mining and science modules, even military, but not economic, influence or morale.... no one wants to visit a crappy mining colony on a dead world! lol