I think it is an interesting idea, but would work better
in theory than practice. Here are my main concerns:
I am more likely to take out energy to answer a more
obscure question if others have not answered it. With
this system I would tend to assume that it was answered
and wouldn't answer. I suspect others would do likewise.
Conversely if the question is basic, there are a lot
of people who will want to take the chance to answer one
that they can get, and the hapless questioner would get
a flood of answers from people who could not see others.
I think that some of the most valuable answers given
come as feedback, improvements, and corrections on
answers others gave. This would remove opportunities
for that.
For very short questions it is already fine to use
/tell in the chatterbox, edit your home node, etc.
People already do this.