Why was Franchy moved off of SS to the outfield? Was it because he couldn't field ground balls, had limited range, had poor fundamentals, or had a bad arm? That's probably relevant in figuring out how smooth the transition to 1B would be.
Maybe he was moved to the outfield because he was considered to be too big for SS and with a skillset that would be better suited to the outfield than a corner IF spot (speed, ability to cover ground, basically). In which case, he might end up being an excellent 1B. He's a pretty mediocre outfielder, so I don't see the harm in trying.