I have my old tank and it looks like the sensor is molded into the plastic tank. I have not fully explored whether the guts could be extracted from the molded plastic. Someone could measure the resistance of the sensor at a few points and try to compare to a removeable sensor for use in a custom tank. Probably BMW’s sensor is not unique to this car in terms of resistance, but I am not sure.
This link probably won’t work but realoem does not show a separate sensor. Looks like it is part of the tank.
https://www.realoem.com/bmw/enUS/sho...diagId=17_1194
F10 M5 tank has separate sensor. Obviously tank levels differ. Maybe it is just an in/off switch and that is all you need for a custom tank. If low, a ground is broken and a warning light goes off. Or maybe it is much more complicated and a signal goes to the ECU to pull timing, limit power, etc. Worth researching that.