

The vice president has to invoke the 25th amendment and then needs a majority of the cabinet. The president can fight it and then it takes a supermajority in both houses to not get kicked out.
So not going to happen. There was speculation for a bit if the reason for a Trump/Vance ticket (to everyone but Trump) was that the campaign and superpacs were betting on a 25th and Vance taking over.

From a brief search of articles written on this subject, Fetterman votes with the party around 80% of the time. The 20% has had some real issues, but he isn’t consistently against the party.