My group just picked a Hunter-Killer regiment (which I really like) but I'm not sure how to deal with the guy in the vehicle interacting with his comrade buddy. Maybe he should stay far away while the vehicle is stomping around? Or just treat the vehicle as the PC for purposes of volley fire and so forth?

What do you guys do?

In all honesty a work around I used was a custom house rule sentinel where all I did was add a second seat like a co pilot in a airplane. If he was called shot there would be a 50% chance it would hit the co pilot instead. If you dont like that idea just have him order his comrade to follow him close but when he gets in a fight have him be ordered back and stick close to another PC. This stuff is where you as a GM have to improvise. When the rules dont fit make your own.

You could requisition an oversized 'Baby Bjorn'-style harness for the Comrade to ride in...

You could requisition an oversized 'Baby Bjorn'-style harness for the Comrade to ride in...

Hahaha I think that would be like a impossible command test to force your comrade to do something like that hahahha

I think I'll have the comrade hanging out with the rest of the squad while the character is in the Sentinel and then buddying up with him when not.