A few ground rules:
Republican senators can only be chosen from Republican controlled states. Even so, they must be used optimally for one of two purposes: to conduct enormous reforms in government agencies (plural), or to be appointed to the Supreme Court.
Importantly, if a Democrat senator is at odds with his caucus, and comes from a Republican state, he might be tapped for a less critical role. It would give him a political life beyond his party, but it would also switch his seat to Republican.
President Trump will have to “arm twist” both the senate and the house to get what he wants. Since McConnell will likely remain majority leader, he will probably charge President Trump a premium to get what he wants.
Top priority will be to get a SCOTUS nominee that McConnell will support, and even obstruct Democrat efforts to derail. This will have a huge price tag.
Nuke the filibuster and have Pence preside over the Senate....and if McConnel comports himself correctly, he can be put back in charge.