It's a difficult situation.
If GM wants to take this action I think the other OEM's and teams would be down for it. Corvette creates a lot of fandom and to sit on it for a year would be a tough ask, the sport will survive with no issue though. Either, Corvette wins and many complaints will be made about it being a detuned GTLM/GTE. If they lose, then the question will be raised if it was even worth doing. I see this like the then new Toro Rosso team running a detuned Cosworth V10 in 2006. Many teams were extremely weary about them running a V10 engine, yet it was done in a way to keep the balance in the field.
GM needs to find a way to keep the GTLM cars alive until the new rule regulation changes come about. Maybe find a customer team interested, however will C8.R be a PITA for customers to deal with like thre Ford GT and be more expensive to operate without factory backing? GM still wants to go to LeMans, so I think they will make the switch and find a way to keep the GTE cars running in WEC.
Not to mention, if Corvette sits out for a few years they could lose countless key personnel, drivers, etc.