And how that editor for example will create pvr texture and publish it inside the project? Also, how it will render all things truly identical to the behaviour of the cocos2d? What about preview on multiple devices? Preview in different localizations? I even kept silent for same as on device a rendering text, effects for sprites, blending functions and many other things.
In what way the behavior of all the elements (buttons, scrolling, labels, labels BM, box layouts etc., will be identical same as on device?
SB uses same cocos2d for all this, so that what I'm saying - new editor must use new cocos2d. When you commit any code for cocos2d, you need just update it from git to the editor branch, that uses cocos2d as submodule.
And so there are two options only: cleanup SB and update with new cocos2d or create a new editor, but use for it code samples, ideas from SB code.