I'm probably not the best person to present solutions to the permaboost problem, while I like the afterburner button idea (hold to boost release to stop), I wonder about revisiting the game design implementation of thrusters or power distribubtors.
Modifying power power management to give it 6 pips per section, and giving commanders an extra pip to allocate to their distributor, and 6 pips engines makes the ship fly like boost. Modifying thrusters into two sections, thruster nozzles and plasma propellant generators offers another option. That option is to give commanders the option to outfit ships with the appropriate size of plasma generator for their propulsion system, then fine tune their ships characteristics by selecting different thruster nozzle sets, one might be the best nozzles for manouvering (yaw / pitch / roll but not strafe or drift), another the best one for speed suited for racing. Yet another different set of nozzles might have less speed (both linear and rotational but also have the least drift and best strafe performances).
There's nothing saying that multiple solutions such as push and hold to boost couldn't be stacked with 6 pip per column distributors and the jigsaw thruster setup and or anything else suggested to rework the flight model / boosting paradigm to find a mutually acceptable solution to stop the farcical debacle that permaboost pvp has become, while not hamstringing large ships.