and then back up and engage from long range where their pen drops off and you can win.
Small arms penetration is 1/1/1 for most weapons (all bolt action and semi auto rifles, all SMGs and ARs, with the exception of LMGs) and their accuracy versus vehicles is 100% on all ranges and while moving too. The only difference is that these weapons will have lower DPS because of cooldown and ROF modifiers at range, but in some cases that may be offset by the significant increase of DPS for the vehicle between mid and close range.
In the particular case of Commandos versus 222 it is advantageous to keep distance with the 222 because the Commando Stens have huge ranged cooldown and ROF modifiers, but weapons like the Panzergrenadier STG 44 (they have the same ROF on all distances) deal similar damage to light vehicles on all ranges beyond very close, so against those it can be better to close in more and maximize the LV's DPS.
Though I think parking your LV on top of an SMG/AR squad is a very bad idea in general, because I believe that will give the squad a good chance to get rear armor hits (due to the angles at which they'll fire at the vehicle) which will significantly increase the amount of damage they'll do to the vehicle.