One thing the OP doesn't address is, is the rewrite intended to be black-box or not? If not, then every "rewrite" will just be someone copy-pasting the old code with the new fixes, which seems completely pointless. And if it is a black-box rewrite, then all that tacit knowledge will be lost, leading to having the exact same bugs over and over and over and over again, forever.

I understand that this is all just a thought experiment, but there has to be a better way of framing it that isn't so immediately farcical.