I have some ideas for tools to add to Gameshell to help with open source game development.
Git branch selector - useful for testing out different versions of a game (https://github.com/clockworkpi/launcher/pull/312).
Issue tracker - this is more difficult but could be possible. It catches errors from games and encourages you to file them, if they are not yet filed.
Save and config management - this allows for keeping the ones for playing and testing separate, though it could also come in handy if multiple people use the same Gameshell.