I don't think this would work well. The assumption is that answers are posted in the belief that they are correct. In contrast, proofs are best checked by taking the adversarial assumption that they're incorrect and demanding to be convinced by the prover.
The expectation here is that a question is a question in the sense of something that a student would ask a professor and an answer is an expert sharing their knowledge on that topic. The purpose of asking the question is for the asker to find out the answer. This proposal turns the expectation on its head. It invites questions in the sense of examination questions (i.e., something a professor would ask a student) and an answer is an attempt by a non-expert to demonstrate that they understand. The purpose of asking the question has become determining whether the answerer is correct. I think this is a bad idea.
Furthermore, "check by voting" doesn't work because correctness is fundamentally not a matter of democracy. For example, I recently posted an answer that got voted up to something like +8 before somebody pointed out a fatal mistake. I deleted the answer but, if the person who found the error had just downvoted, it would still be at +7 and everyone else would still think it was awesome. But, actually, that one person's "vote" (as I recall, they didn't even downvote, they just commented) invalidated all the +1s.
Problem-dump questions are generally uninteresting so few people will read the answer and actually check it, especially if it's more than a couple of short paragraphs. Is the answer at -1 because somebody didn't like it or because they found an actual error? (Or even because some people object to self-answering and think it's just an attempt to gain rep.) Is it at +2 because two people checked it carefully and found it correct or because one person skimmed it and thought it looked more or less OK and somebody else piled on? Or, as outlined above, because three people thought it was fine and one person found a fundamental error?