“What if Trump forces Prince Pubus to FIRE RYAN? “
The Constitution provides for three separate branches of government. The President, and his staff, have no power to appoint or remove members of the House of Representatives. Only the members of the House of Representatives, or the voters in his congressional district, can fire Ryan. There will be an election for Speaker when the newly elected Congress convenes in January. If you want a new speaker, lobby the Republicans elected to the House for the next term to make a change.
As to the choice of Priebus for Chief of Staff, from what I’ve observed it was an excellent choice. Priebus stuck with Trump and did his job to elect Republican candidates despite tremendous pressure from the GOP establishment, the media, key donors, and many GOP politicians to denounce Trump. Priebus knows where the bodies are buried in DC as well as the inner workings of the city. Many GOP politician owe Priebus favors. This knowledge, and leverage, will be critical for Trump to hit the ground running. In addition, he knows the donors intimately and can be effective in bringing those who bailed in 2016 back into the fold for the 2018 and 2020 elections. Plus, as an insider he can tell Trump which potential candidates for jobs in the administration are likely to be loyal and which will be backstabbers or leak to the press.
Which is exactly what the WH with its immediate access will do and, IMO, will do quite successfully. (For example, see Valjar.)
As for the rest of your #128, I agree completely. It somewhat reminds one of the circumstances of Gen Eisenhower's appointment as Supreme Commander.
Priebus will be acting as gatekeeper and thus may wield a great amount of influence. However, Trump will be able to monitor exactly who has expressed a desire to meet with him and for why and which of those Preibus admitted. It will operate very well, until Trump may sense it isn't.