Feds have no sway in that regard. Trump could legally end up in State prison.
Something would have to be worked out, to allow the Secret Service to provide him some protection in the yard. Unless they were stripped of all presidential privileges. I suppose the process might be no different than him revoking citizenship a certain immigrants.
Then it would be perfectly appropriate, for him to end up as someone's prison wife.
That's why I suggested house arrest. Trump's penthouse is perfect. Reprogram the elevator so that he can't call it. Make it stop on the floor below so that it can only go higher or lower if sent from there. The SS & NY state prison guards can amuse themselves playing cards & etc on that floor. Alarms on the fire escape. Telephone land line only (no twitter). No internet. TV. Defined visiting hours. Conjugal visits for Melania. Maybe golf furloughs a few times a year. Enclose the balconies so he can't jump when it drives him nuts.