I'm not arguing for or against, but:

> You will lose all of that in a rewrite

I don't think you lose everything in a rewrite in general - you still have all of the edge cases and business logic in the old code that you translate to the new code. It's not like you are implementing whatever it is from scratch.

Sure, there are opportunities for the translation to introduce regressions, but that's a vastly different argument (and I think a much more minor downside).