Should you move into deeper / longer / more challenging diving, would you consider your sidemount rebreather to be the basis of a bailout rebreather? Thus removing the need for lots of additional bailout cylinders?
Not at this point.... carrying 3 bailout cylinders is the most I would carry with the sidemount unit (not including the LP85 DILOUT).
Moving deeper with a backmount unit, that would be at least 4 bailout cylinders worth of gas (plus the rack on the back) before I would even consider the complexities of using a BoB... still quite a ways away, if ever (...... famous last words)
This is all open water.
_R