This is always an option, but more often than not it will interfere with your own play. If you have to pick up his MG, that could mean your team is down an Engineer, for instance.
Unless you drop your Engineer weapons, sure.... but since you have carry two primary and two secondary weapons without having to worry about your equipment/grenade loadouts, the only thing you'd really suffer in is the additional weight that slows you down and reduces your stamina.
But once in a while I've been known to pick up an MG, go clear some road blocks & obstacles, then when I was out of Engineer equipment, I headed to the closest wall or sandbags and setup the MG for suppressive fire & support...... when I came across an ammo cache, I'd switch back to my Engineer role, but also still able to switch to MG when needed.
Or Marksman, or Anti-Tank Class, etc.
Fortunately, the MG unlocks (at least as a German) incentivize proper use to a degree.
True.
In general, though, this kind of rank-at-all-costs mindset does result in several issues.
There's a positive aspect to the progression system too, though, don't get me wrong (some people have figured out just how much capturing/defending objectives goes into leveling, and machine gunners rarely go un-supplied on spawn).
True.... for me, ever since the mod days, whenever I see an MG anywhere on the map, I risk my life to chase them down to resupply them as it has always been an easy way of getting some points, while also helping them out.
You do get an assist point for inflicting damage on an enemy tank--it works somewhat inconsistently, however. I got one today for landing a non-fatal AT nade on a T-34 seconds before our tank finished it. Your point, though, is valid.
Yeah I have gotten assists from time to time, but it's rare and most times I end up with no points for the damage I have inflicted.... even so, one assist point for several damaged areas of the tank I inflicted just doesn't seem like much of a reward.
My speciality with the ATR is taking out tracks.... no matter what angle or distance, I always get them stuck in one spot.... now I just have to figure out how to disable the turret consistently.