What I would do, is fork SpriteBuilder, make it compile, and release it with the official cocos2d.
However, it is a huge task, and SpriteBuilder is in many respects a can of worms. I mean. What were they thinking when they designed the resource system? It is a train wreck.
The front-end though, has many good ideas, and it would be a great asset if anyone could get SB to work with new cocos2d releases. SpriteBuilder is much better than CocoStudio, so at this point it is actually the best shot at a serious cocos2d front-end. Imagine adding -x support, and you could probably even make a good living from it.