That sounds like an awesome role! Supergreeting sounds really fun.

You said a lot of CMs are cross trained with ToT, RnR, and Beauty and the Beast - were you referring to all HS CMs or just Fantasmic CMs? I really like the idea of being cross trained with another role, so that hopefully it would seem a little less monotonous, but I had read that it was really rare for CPs to be cross trained. Were CMs automatically selected to cross train, or is that something you can request?
Thank you to the people who answered regarding back problems. I hadn't even thought about the lap bars. Bending over generally isn't a problem (although I've never done that as much as I would if I worked, say, EE) it's mainly just repeated or heavy lifting. I was thinking that ToT (just for example; I know better than to pin all my plans on getting a specific attraction) might not be terrible on my back. ToT, if I remember correctly, they just have people pull up on the yellow tabs. Plus, as was mentioned, the shows would work well.
If I know going in I need to be placed in a role that is easier on my back, do I need to have documentation from a doctor?