This is more a general question of how you handle them.
Because in my mind, they won't always have a vehicle.
Making their vehicle use infrequent makes the specialty not worth it, while if you want them used often, you have to tailor your campaign around the fact they have a Leman Russ with them.
It's just that, in my mind, V-Scale and P-Scale can be very separate.
So how do you plan around this? What do you do as a GM?