The 460 would be a terrible choice. It may knock him right out of the tree stand.
I have a BFR in 460 and it is a handful. From my experience with Condenders(which isn't a lot, but I've shot them), they tend to kick more than revolvers. I don't think I'd want to drop the hammer on a 460. I've shot my dad's 30-30 Contender, and that is a nice round out of them. Quite accurate and recoil isn't bad.
You can shoot 454 Casull and 45 Colt out of the 460 barrel, but accuracy may suffer. It does considerably in my BRF. The 454 would still be brutal. The 45 Would be a decent round, but it would be pointless to buy a 460 barrel just to shoot the other calibers out of it. I think there are better choices. 22-250 or 243 might be other good candidates.