Can multiple people be in same tank?
Yes, but the person bringing the tank to battle must order his soldiers to get out first. Then real players can take their place. You can also fill the empty seats in your friends tank when his crew gets killed.
so if my friend got in the loader seat how does that work?
There can be 3 seats occupied: gunner, driver and commander. Rest is filled by AI.
Yeah, I can confirm that despite being 5 sits available per tank, only 3 are accessible for players.
Driver, which he can drive the tank,
Gunner, where he can shoot, and lastly,
Commander sit. This last can watch through observation points, and use roof machineguns ( only Normandy later tanks )
The loader and radio operator basically works as spawn points in case you lose one of your main core members and not accessible for players.
Hope this can answer, cheers^^