In feudalism 3 you should be able to upgrade the amount of troops you can have in your army, in stead being bound to a certain limit depending on the difficulty. Of course their should be a limit to how many times you can upgrade, but it would be cool to steadily hoard troops as you progress through the game
More clipping on your ship would be a great addition. The best part of top-down shooters is the dodging, and it's quite difficult, even with the smallest ship.
glitch: I had spent some money in the shop, went out to do the next lvl, died, and found i had the thing i'd bought, plus the money i had before i bought it.