I think if it doesn’t specifically display the words “OVERHEAT!” or “COOLANT APPLIED”, then it shouldn’t count against the medal because the medal only says “not overheating” (although the weapon description does say “when overheated”, I don’t know). Not overheating is only worth 20,000 points, while you can already miss so many enemies on using it to go for the medal (and I don’t think many players are interested in farming this medal anyways).
Reworking on Corn is fine too, but it’s not as cool as keeping the coolness medal. This needs discussion though, you should undo this change until the Corn stats are finalized.