A subtle point, maybe.
The AI presently rips apart your infrastructure when it starts a war. Shipyards, starbases, asteroid mines, they would destroy your rally points if they only knew how. I understand that. It's what I do, and they are almost as vicious about it as I am. (Trash talk aimed at Frogboy and his AI) However, I have taken to not destroying an opponent's asteroid mines, because I see them as being mine when I take the planet. I think, especially on higher difficulties, the AI should reconsider the destruction of asteroid mines if it intends to invade and occupy. To me, the easiest factor would be: if I have transports in route, stop destroying asteroid mines. It might depend on being aware of its own future intentions and planning, but generally, if the human player finds it a terribly obvious notion, the AI should, too.
Of course, all this would be moot if asteroid mines didn't switch with culture, but I like the idea that the miners don't care about our Imperial ambitions. They will do business with the gang that says it owns the turf. It doesn't matter who it is. My kind of people.