If concerned about question 20, why not change
the wizard's "power" altogether. You could let them
have "telepathy" whereby they can answer for another
player after a neg. If that sounds too weak, you could
let them "turn back time" by being allowed to buzz in
any time between a neg and a correct answer. If
they're right, the neg goes away and they get the points.
If they're wrong, they get the neg instead of the
original player.
By the way, I can't believe I'm
actually writing this. ;)