Invade Cuba.

Certainly not outside the realm of possibility. What else is he going to do for the next 2.5 years?

He's burned through anything he could get through Congress - including possibly any nominees that aren't straight middle of the road. He's never lived in a company with an independent board of directors - and while that's not exactly what Congress is vis-a-vis the President, it's a useful analogy even though it's wrong in the details. He doesn't know how to handle having to get someone else to agree with what he wants to do before he can do it. Not having any Congress-whisperers in his Administration let him thrash around unchained (which he wanted to do), but now he's paying the price for not doing what all his predecessors were smart enough to do. He was able to get away with finding whatever emergency powers were tucked away in the statutes on a temporary basis - but now that all those lawsuits are moving past the initial stages into the permanent injunction phases, those openings are quickly being closed. Justice moves slowly, but eventually the courts issue final rulings.

The only levers that are really his and his alone to use are the foreign policy levers. So if he doesn't want to spend the next two years sitting in his office stewing about how the Senate won't do what he wants, he's going to have to do some more foreign policy adventurism.