I think Trump will base his actions on the Israeli position (which doesn't give Gaza any territorial rights in international law).
If that is correct, then Trump can adopt that position internationally at the UN. He can support Israel at the Security Council by effectively not agreeing any action except this solution.
Eventually I assume then unless other countries were prepared to land troops in Gaza it would become a fait accompli. Who would intervene?
Even if the above does not work, then Trump could agree that the US leads UN deployment of troops. That gives him the same control.
Or, solution three. This suggestion he has made is so outrageous that the countries bordering Israel make their own arrangements for the Palestinians who will be leaving. Btw from the sounds of it, this is preferred option and the cheapest.
All of the above utterly tramples on the idea that Palestinians have any rights to a sovereign state, or a two state solution. But that too is a matter of agreement. If the US gives up on even looking fair then the above seems plausible.