You can use it how you want but- a tip I found on my big printer- keep your physical limit switch and wire it into the motion board as an "Oh poop" switch.
It is possible for scenarios of a BL-touch to fail (example, not over the bed, bracket bent or melted, wiring failure, etc). You CAN and WILL then ram the bed up into the nozzles unless you also then wire the old limit switch in some way to kill the machine- example wire to reset of the motion board- thus killing the operation. You do it such that under normal logical conditions the Z limit is never hit, but in failure, it gets tripped. By reseting the motion board, by definition- the Z motion will stop- no special firmware version required. I say this because again, I have seen both conditions possible and had I not been right there, bad things could have happened. Not to mention, adding wiring that flexes to the printhead to wire a Z probe is asking then for a future failure. It's not if it fails, it's when it fails. Be prepared.
Again, my advice.
Do not attempt custom firmware unless you really know what you are doing and then test it over and over.
Not worth the effort of trying to remap the Z- limit switch location to some kind of emergency stop in firmware. By definition, again, asking for failure. You re depending on code to read a pin status and do something.
Opposite, moving the old mechanical Z limit switch to reset pin and ground (2 wires)- relatively easy, and extremely robust in that no matter what firmware is loaded, I assure you motion will stop. This leaves you then with standard wiring, pin configuration, and firmware from the BL-touch example others have installed. Obviously, what you will do is lower the thumbscrew the bumps the endstop switch slightly, such that it only trips when the nozzle kisses the bed slightly. It's a fine line touch but again, the idea is to prevent a full on rising bed jamming into the nozzles and continuing to drive upward when the BL-touch fails to sense.