Since C2 is completely internal your only option for collaboration is SVN, which I feel is overkill if you're only using it so, say, your team can collaborate on levels.
That said, maybe we can have the ability to save layouts individually like some other engines do? And an "update layouts" button to apply changes made by team members? This way, if the project is on Dropbox or something similar, team members can work on levels at the same time without overwriting everything else or having to reload the whole project to update other team members' changes.
Sure it's not the *perfect* solution but it seems like an easy way to allow teams to work on levels together without the hassle of SVN.