I asked about SB because all what we need or can be done already done in it. So, we need just copy it. And that about you talked here http://cocos2d-objc.org/the-magic-layer/ - is completely the same as in SB already done. So, I don't see any magic...
I'm assuming that you never worked with SB?
In my previous post I showed Bottom-left, Top-left, Top-Right, Bottom-right. Does it make sense?
That car with +20 pixels is no problem with that.
Now, I realised you have never worked with the SB. According to commits to 3rd cocos2d-spritebuilder you know little about it and only now beginning to learn something. All were done by @slembcke @vik and other people. But it's no matter for me now, I just want to help you. But I think that it's not fair to call old things from SB like new or magic in some new cocos... even if you wan to rewrite with new lines of code, result will bee the same.
I'm sure that it was necessary to support all of these options:
However, I never used: UI X in UI points or With inset. Just: X in points and % X in percent of parent is all what I need and all it already works in SB, as you call it magic layer.
Also, same already done in crappy and laggy cocos studio: