[illuminateddan]

Surely if your controller goes over current you want it to switch off until a system reset can be done. If a mosfet fails closed and causes an over current failur then you want the system shutdown ASAP before you get a cascade failure of the mosfets. Check out the open revolt cougar controller overcurrent system. Pretty straight forward with a power down to reset system.

 

[illuminateddan]

If I could build this with 3 or 4 parts why buy that board with 100 or so parts on it?

Because the other 96 parts do other things, from opto isolation, stabilised power supplies correct signal formatting (with pull ups, pull downs, diodes, etc) and many other things. Good luck with the 4 parts. you'll need it!