I doubt this would ever happen, but if Kings Island doesn't plan on removing Invertigo anytime soon, would it be possible they could order a new train from Vekoma? It would be similar to how some parks have bought new trains for their SLCs, though obviously it would have to be modified to be able to work with a Vekoma Invertigo model. The park could also tie this in with a retheme to Screamin' Demon to pay homage to that former attraction, which also went forwards and backwards.