Rand Paul would be a good choice. Definitely in my top 5.
He knows the system, has successfully fought the system, and has retained some semblance of respect amongst his colleagues unlike Sen. Cruz. He also brings in a lot of younger folks, and would be bringing in his horde of operatives which is no small feat: they’re tough and they’re fighters.
If you survey folks based on their political views you’ll find that a plurality are neither conservative nor liberal, but of a more libertarian bent.
Knowing how Trump is he will probably get someone totally out of the blue that none of us has even thought about.