I'm starting to think that the 105mm-armed LAV-"75" would be a pretty ideal PC vehicle.
First off, it's 105mm gun is powerful, but would need to be skillfully used against T-80 and later MBTs. Ammo for a 105mm would be scarce, but not impossible to find. Also, with an autoloader, no PCs crewman would get stuck with that thankless job (and/or you wouldn't need an NPC to do it).
Second, with the same basic drive-train components as the ubiquitous M113, there'd be enough spare parts out there in the game world to keep it running throughout the campaign.
Third, it doesn't have the same type/degree of high-performance composite armor that the M1/Leopard II/ Challenger have, meaning that the PCs will have to avoid risks that having "magic" armor might otherwise encourage them to make.
And lastly, with it's remote turret, a turret hit would not necessarily result in the death/incapacitation of the crew.
Of course, three PCs would be a pretty small group. The LAV-75/105 would work best with another vehicle or two. A companion M113 would be pretty ideal due to the commonality of automotive parts. It's lighter armament would be useful against soft targets, while the LAV-105's big gun could take on armor or harder bunker-type targets.
Thinking about it really makes me want to run/play in a campaign featuring a PC-crewed M-20 Ridgway AGS (i.e. 105mm-armed LAV-75).
