If Trump were to engage in a massive aerial campaign over several months targeting all regime leadership, all IIRGC facilities and all their leadership, regular military and police facilities along with western special forces on the ground could it be enough to topple the regime? It would almost certainly end the nuclear programme for good. Going after all ballistic missile production facilities as well. If this is not enough then destroying key industrial/transport targets such as oil industry and ports. I feel if nothing is done the regime will remain in place and very likely end up with nukes.
There does seem to be a possible leader in waiting in Crown Prince Reza Pahlavi. I certainly heard his name mentioned by Iranians in protest footage I have seen.