Neat idea. Reckon the hardest bit would be getting the lintel in just the right position on the wheel so that it would clear both the adjacent lintel as well as its awaiting tenons before being dropped onto them - bit of precision manoeuvring needed there. But then how would they roll the wheel back out once the lintel was in place? If it did work though they'd have been able to just move the wheel and its track from one pair of uprights to the next.