The bakers racks I got from peachsuite have nice big locking casters, you can lock/unlock with your toe pretty easily. They're cheapo at around a hundo per but plenty sturdy loaded with 23x31 M3s with pin locks.
If yer going to go for the pass through make sure there is a nice, smooth, unobstructed path for the carts. Wet rooms and coat areas tend to have rubber matts and dragging those loaded racks across them is a bitch. Make a racetrack for the carts basically and it should work out gangbusters.
I drew up plans for pass thrus at our current space but found we didn't have enough overall space, it takes a good bit more than you think to work efficiently, but then again what doesn't?