As long as its DC this is very easily accomplished with 2 relays. The biggest thing here is the relays will need to have both 87 & 87a poles. 87a being normally connected and 87 being connected when 85 & 86 are energized. Majority of 12v relays are only 4 pole.

EDIT: Here i used to do this exact same setup to reverse polarity to power door lock actuators. Heres a diagram



Substitute your switch to ground for the alarm lock/unlock outputs in this diagram, and the actuators output as your motor.