First off I'll start by saying I've absolutely loved playing the game this week and I'm truly thankful for the time and effort you've put in to making a very nice RTS with some original concepts. The market system is fantastic.
I've played around 30 hours now and feel I have a good enough grip of the game to give some reasonable feedback for you.
The main downside I'm finding now is game play at the later stage between two players who have a good idea of how the game works. There is very little you can do to reverse the inevitable defeat and it tails off in about 10-15mins of off world market launches. As long as the player uses goon squads nothing really can be done by the opponent. Another idea to make the end section of the game more variable is to add a level 6 with one claim and with level 6 the ability to build a tourist hotel. I would also add one randomly placed "land mark e.g Olympus Mons/ Valles Marineris per map with the tourist hotel revenue correlated to the distance from it. That way at least if you are lagging behind someone slightly on off world market battles you can risk it all to go after the tourist hotel and level 6. I think balanced correctly it would work well?
Also a second point is that a good player will ALWAYS judge what and where to play as by looking at the colony city at the start. If it's glass you should go robotic, chemicals scavenger etc etc. I feel that the colony city needs more random events or influence by the players. I think a great way to deal with this is maybe through the black market to sabotage the colony or to "donate" a module of choice to them. You could also add natural disasters that take out some of the modules.
Overall I couldn't think of a better concept for a game but without addressing some of the later game stage game play the playing experience (at least for me) kind of plateaus after about 25 hours of play.