I'm not sure I understand what you are proposing.
For each section of track that you want to block detect, you would run that bus wire through a block detector like the NCE BD20. That same section of track would need insulated joiners or gaps in the rail that has the block detector. Since the layout already exists, you would cut gaps.
You can still use your circuit breakers. The circuit breaker would come before your block detector. Your circuit breaker can provide power for multiple blocks that are being detected.
You cannot put your circuit breakers after the BD20's. The little amount of power drawn by the circuit breaker would make it look like the block is occupied.
Wiring for DCC