I think a good expectation for Caissie (or Mo) that toes the line between optimistic and realistic is something like Michael Busch's rookie year. Michael Busch put up a roughly 120 wRC+ as a rookie, and that game with the benefit of significant platoon support.
Busch, like Caissie, took two go arounds at AAA. Busch, like Caissie, improved significantly his second go around. Busch, like Caissie, very much felt like he had mastered the level when he finally got his cup of coffee at the MLB level. Unlike Caissie, Busch was able to get his K rate under 20% in his second go around, which led to him being a tier better as a hitter at AAA. That said I think that is balanced, hopefully more than balanced, by being three years older at the same career step.
But Caissie just being 1 for 1 a Kyle Tucker replacement is probably something like a 95th percentile outcome. It's not impossible but if we're already seeding expectations there then this highly petulant fanbase is going to eat him alive. Let's not do that.