I currently like the achievements that you get, but I have three suggestions:

First, have a score for each game to compare previous games to the current game.  This was one of my favorite parts when I play one-player strategy games.  I always want to see if I can run up the score.  This is why arcarde games were and are still popular.  It is a tangible goal, even if you are the only one that ever sees it.  This could be a realitively easy future patch update.

Second, make the rewards into some sort of visual goal as well.  Some of the console games really turned me onto this.  Super Smash Brothers have trophies and Drake's Fortune have treasure that you collect.  It is the equivalent of receiving a trophy versus a piece of paper.  This would be a great addition to an expansion pack since it would require the company to hire someone.

Third, have some sort of end game cinematic.  Right now the game ends and it feels like I got a "thumbs up" versus a standing ovation/applause.  Again see suggestion one regarding running point total.

These are just little things in the grand sceme.  I hope people agree with me and take these suggestions to heart.  I feel that the gameplay is solid and that it definitely fills my sci-fi strategy needs!  Thank you for a well-executed and fun game!