Personally, I think the Republicans won't break ranks at all during this. That's not to say that they won't necessarily vote to remove Trump, but if it comes to that, I believe they'll publicly support Trump right up until the moment they pivot as a whole to vote him out.
The only way they save face, as a whole, is as a whole, as it's unlikely that the Republican voting base can blame the entire Republican legislature for not being "Republican enough". I think Mitch is secretly using things like the Syrian mess to sow the seeds for a future break from Trump, and I wouldn't at all be surprised if he made sure that his people stepped out of the way prior to Trump's Syrian hijinks for that specific reason.
Or maybe I'm just ascribing too much Machiavellian thinking to Mitch, who knows.