This isn't about whether he should be done or not since we all agree that new molds are better than remolds. But what if it did happen? He'll get a new head of course. I think the vehicle mode would work even with Perceptor's treads. Perceptor's shoulder-cannon would work too since Trailbreaker had one too in the cartoon (on the same shoulder, no less). The chest could be painted to be similar to Trailbreaker's vehicle kibble. Perceptor's clear chest part would be half painted over so that the 'windscreen' part of Trailbreaker is narrow.