I've got a MVS conversion cart of sorts, just not by the way you're thinking as no AES was brought into it.

What I have are a set of legit SNK boards that had a wrecked set of chips and they were removed, and those were replaced by some arcade supplier with gated EEPROMs with another game installed. That though interestingly is put into a modern black clamshell (not an original of the 90s) and has a decent quality replacement sticker on the front. It didn't cost me much at all which was fine by me as Nightmare in the Dark isn't cheap. At least mine recovered 2 boards and cannibalized nothing.