I definitely see where this feature request is coming from, but I think it may be inadvertently treating a symptom rather than a problem.
If a question is edited so much that it makes existing good answers bad or vice versa, it's likely — just likely, not guaranteed — that something was wrong with the edit. It could be a case of an editor accidentally changing the question's intent, or it could be a confused new user trying to ask another question. In those cases, action should be taken, but resetting the votelock isn't the right action.
On the other hand, the edit could be the OP updating with an "I tried what user 124390 said, but it didn't work" message or clarifying an ambiguity/typo. In those sorts of cases, resetting the votelock could be appropriate, although it might be better to just have the answerers delete their posts.