One thing that I think would be great is to take advantage of some of the stuff Apple is doing in SK, like adding support for sprite sheets generated by Xcode.
I had an idea awhile ago to create an app that would create sprite sheets, but you'd do it in the same way you do when you create an Asset Catalog for a 'regular app'. I didn't have the time to try to make it; I'm glad I didn't now (if you've seen the WWDC video on what's new in SK you'll know why).
I only tried to make an SK game once and hit a bug in the framework pretty early and decided that i wasn't going to try to workaround the problem so I stopped. I know the sprite sheets are created at compile time, not sure if Apple makes it easy to access if you aren't actually using SK or if it would be a nasty hack (if not, I think it would be nice to have Cocos2d work with it).