for me, kicking out ideas is perfectly fine (and a good inspiration as well) which is exactly how i came to do the J&SB edit. dhr001 (IIRC) originally was going to do it, in the end nothing came of it, i asked him if he would mind me doing it and the rest is history.
but like Throw said, blatently setting an edit plan out and then just asking for someone else to pick it up is a bit cheeky.
i think maybe the best way to not step on anyones toes is to flat out ask the editor if they are still planning on doing it. if you get a reply great if not, then after a week its fair game again.