in my opinion, this can be achieved in wave
the problem orignally starts in one wave
people can discus each idea as a tangent to the proposition
when the idea becomes sufficiently fleshed out
move to another wave dedicated to it
everyone interested in working on it can jump into that wave
and this could be repeated as necissary
I see no reason why this wouldn't be satisfactory
my biggest issue with wave is the speed
at least when I was using it heavily