change ownership of Personal Apple Developer account

it occurred to me that re-signing the app under a different developer license would effectively kill the existing app on the store.

This is false. As long as you transfer the app like Apple suggests (you need to contact them for this), the company just needs to submit a new version from their account and it will work. You don't lose your ratings, nothing. It all gets transferred to the new account including the iTunes Connect side of things. They can sign it with a different certificate and submit. As long as the app ID is the same as before (which it will be), there is no problem.

It sounds like you have old or inaccurate information, because I know somebody who did a transfer like this, and they kept all the ratings etc.

I have faced this same issue, after contacting apple several times, we concluded that there was not other choice, so we removed the app and re uploaded it a gain on the other account

Not only the rating has been wiped, but also users with old app will not be able to update it when you push a new version to the app store

Its a very tough decision, but we had no other choice