My only thought about getting around this is to run one installation of Aurora that has four (or more) dummy games, one for each category, that point to other installs of the Aurora dashboard. Each installation you make will only scan a single folder (One folder for XBLA, one for Games, one for homebrew, etc) and therefore separate your game library between installations. Then simply launch the corresponding dummy for XBLA, GAMES, HOMEBREW, OGXBOX, etc. That way when you launch whichever category you've picked it will only list the games for that category and help you stay below the current limit.
I know that's not quiet the workaround that you're going for, but it might be the best that can be managed at the moment.