In fact, you need to add few things to make it stable and safe.
There're no gate discharge resistors.
Resistors values are too high, or at least in simulation had very slow switching times, several 10s of ms.
Applying 12V at the gate 12V is ok, but it allows up to 20V, so I suggest using 16V for lowering Rds even more.
I don't see how you could simplify the circuit. If you need reverse polarity protection, you need a second transistor, otherwise the current would pass through the body diode.