I think there's definitely at least two factions in the GOP. Trump is now de-facto the leader of one of them. If the other faction tries to dethrone him and put Pence up there instead, it absolutely will cause a power struggle. The reason that Ryan can't put forth an Obamacare replacement is that he can't get all the GOP factions to agree on one. To impeach Trump, Ryan's faction would have to enlist the Democrats. This would be seen as a betrayal by Trump supporters, and would cause a problem for some time.
Now, would the monied faction really risk their congressional majority for a Pence Presidency? As long as they can keep some semblance of unity, they have all three branches. If they take down Trump, they risk alienating his supporters and having to rely on Democratic support for any action they want to take.
