There is already a mechanism that requires sufficient rep to edit answers. If your rep is too low, then edits go onto a review queue instead of just happening. That lets others who presumably know the system more than someone with low rep decide whether the edit is something that should be allowed.
This apparently worked, since you said it was a pending edit. In other words, the system didn't let him edit your answer. The person was only able to propose an edit. Apparently this happened recently enough before you logged in that the edit hadn't been resolved (rejected or accepted) yet. You as the post author can single-handedly reject a proposed edit. It looks like everything worked to properly deal with a bad proposed edit.
I don't think we need more than we already have to handle edits from new users. This really has nothing to do with whether the user is who asked the question the answer is for is the one proposing the edit. Some other moron could have proposed a bad edit too.
Bad edit proposals that alter author intent get rejected pretty reliably. I've seen a few of those on my posts over the years too. Often they are rejected before I even realize the whole thing happened.
In the rare case where a new user manages to edit one of your posts to say something you don't want to say, just roll back the edit. If it persists, call it to the attention of a moderator.