Heh some very good suggestions here
Of all the game I've made, I like those 2 particularly too. This year I'll be quite busy with USM2 because of the soccer World Cup, but after this summer I want to go back working on those games.
Well, Magic Stones will have the new quest very soon (I'm finishing it right now, shouldn't take long) but Supernova could really use some of your suggestion. About them:
1) definitely I want to make a true campaign, with multiple choices and endings, and so on. I think I might even do something more strategic like Galactic Civilization or Star Control (two games that clearly inspired me), still keeping the arcade battles though.
1.5) another cool idea. I would do character development too, like a rpg, with various skills (gunnery, flying, etc). Or even hire a team for each mothership so basically you could change the weaponry but also have bonuses based on the crew skills.
2) yes that's a thing I should have added already since version 1.0
3) see above
4) well I know about multiplayer. the problem is that technically speaking, making multiplayer real-time games like that one is quite hard (indeed you won't find many). A solution could be just have a local 2 player duel mode in supernova, that would be easier to do (without scrolling screen).
Strategy games like Magic Stones should be easier to program for multiplayer, and I could add that feature in near future.
Thanks for the suggestions as always, going back to work on the Ice Queen expansion