As it stands the M-8 can go after lightly armored targets; M-16s, M-3s, LVTs, and other M-8s. It can damage Panzers, and Shermans, with difficulty, and a well placed shot will kill them. However it can not damage Tigers and T-34s. That little 37mm popgun can not penetrate the thick armor of the Tiger, or is deflected by the sloping armor of the T-34. IMHO the M-8 trades firepower for speed, wich makes it a balanced ride.
Look at how the vehicles are balanced speed/firepower wise. You will see that the fast movers are the most lightly armed. Hitech has ballanced vehicles to the point where you have to choose: Do I want to get there quick, or do I want to kill everything that gets in my sights.
If you introduce something like the M-18 that has speed and enough firepower to take on the "BIG" boys, you will fundamentally change the game ballance. I don't think Hitech will go for that.