Well it would be difficult to "half stay" so yes/no was the right question
I have forgotten so I don't know the answer here, but was there a detailed proposal outlining what powers these new assemblies would have? I assume there was. So at least people understood what Yes/No would mean.
That was easy then, just deliver what was in the proposal.
Brexit could not be easier just deliver what was in the proposal.
But oh wait nobody thought to write one.