I've done a little reading on state machines.
I guess the tables for this would be as follows. completly scrap the brakePin, and instead use a 10 minute delay, if the user isn't in the car with the key in and switched to ON, then bad luck, he/she has to start the vehicle again.
State0: onPin = off, ignitionPin = off, alternatorPin = LOW.
Upon recival of serial command, go to state 1.
State1: onPin = on, ignitionPin = off, alternatorPin = LOW.
after 5 seconds go to state 2.
State2: onPin = on, ignitionPin = on, alternatorPin = LOW.
once alternatorPin becomes HIGH, go to state 3, if alternator pin is alrady HIGH, go to state0 (in case if someone floods the serial)
State3: onPin = on, ignitionPin = off, alternatorPin = HIGH.
once 10 minutes has elapsed go to state 0
Does this seem right?