The problem with breakwires as a staging timer trigger mechanism is that they are prone to accidental triggering. You need some kind of secondary safety, maybe a pullpin power switch, which would be the last thing that you would do before you leave the pad area. With an accelerometer and/or baro-altitude check, that can't happen. [Shameless plug: The Eggtimer Quantum will do the staging function, has breakwire verification and baro altitude and/or velocity qualifications, fits in a 24mm tube, and will light an Aerotech igniter (depending on your choice of battery). It can also be armed remotely via WiFi/browser from your phone, 100' away from your rocket. The kit is $40]