Terms are a starting point in negotions. Both sides of the table have terms. It not about what crumbs one side offers, it's supposed to be intelligent people working out what's best for all, unless one side has an axe to grind about the other side leaving the club, and simply want to cause problems.
Meanwhile no one can predict with certainty who will be voted in leader of a party, and thus PM, when some loser resigns.
I know some folk exist who like to claim everything must be analysed in the minutest detail and planned for before starting anything, but in reality one has a goal and has to adapt to circumstances as they arise on route. Voting for what is right is the correct thing to do, not cowering in fear of doing anything because one can imagine issues.