A good feature would be to be able to automaticly extract and play (with emulator of choice) roms from GoodMerge archives. Also it would be nice to be able to set a default region, for example if you mainly want to play US-games you could display only the game-title in the UI, and when you "launch" that game, it automaticly extracts the US-version and launch it. OR you could simply make the UI look like MameUI, where the preferred version of a game is shown first, and then indented under it is all the clones (other regions, hacks, etc), like this:
(example taken from MameIU)