Use a separate 24 V power supply for coils. It will also minimize interference to logic voltages. Design coil drivers as open collector NPN outputs, and they will work fine with 24 V coils.

It is much easier to use the open collector NPN output, to ground the coil while its other side is connected to coil power supply. Then you don't have to care about the coil voltage on the logic side. The driver transistors emitter is connected to ground, and you just supply voltage to transistor base (via a suitable resistor) to get the collector pulled down to ground and activating the corresponding coil.

I suggest copying the driver transistor and its pre-driver scehmatic from WPC driver board. You might also just try using a TIP102 or TIP122 Darlington, and driving its base from your Arduino or whatever, via a 1k resistor.

Remember to install a diode across every coil (the banded side to coil voltage, other side to driver transistor output)

True that! Someday I will have to get out of the '70s and remember to use modern components...