Simply not the way accelerators work. An accelerator doing that would need to be using additional energy for the backblast. The heat in a PPC is for the power that's necessary to accerlate the particles. An RPG (sorry, bazooka is just to silly sounding I can't use it un normal conversation without wanting to laugh) accelerates using a rocket, which vents it's energy backwards. The backblast is so the soldier firing it doesn't take the force from the firing and get knocked on his ass.
An enlarged variant of the Plasma Cannon with an option to take additional heat to the firing unit, or to take a piloting roll might work ok using the concept.
EG
Large Plasma Rifle (experimental)
Damage 15, Heat to target 1D6+3, Tonnage 10, Critical Slots 3, Range 2 minimum, 6,11,16, Ammo per ton 7, Heat 17 or 10 plus firing mech must make a piloting roll, this is at the firing mechs decision on firing time.
PR's are made with a +1 bonus if the Large Plasma Rifle is in an arm wich allows for more flexible movement. The firing mech's mass also
affects teh piloting roll, with Light mechs -1, medium 0, Heavy+1, and Assault mechs +2 on the roll made.
If using the higher heat option:
Infantry in the same hex as the firing mech will take 1d6 damage, Powered armor will take 1 damage (to all units in the powered armor squad) Terrain in the firing mechs hex may be set on fire as though it had taken a flamer hit.
The Large Plasma Rifle is a Capellan Confederation prototype weapon being battlefield tested near Republic borders. It has recently undergone a fallback when the lead engineer in the project was killed while checking on the heat expansion systems in the weapon on a firing range. The weapon shows promise, but the drawbacks are signifigant.