The Germans used Ammo carriers to supply ammo to the tanks...that would be a cool addition having a Sd.Kfz supply ammo to the tanks on bigger maps..they would pull up next to the tank and resupply the ammo.
First I run out of ammo many times...I even run out of ammo with the K98 which I can carry up to approx 11 clips...in addition there are times where infantry are pinned down in areas and cannot reach ammo dumps, also you can move troops approx 4 troops with this type of carrier...in addition of course tanks were resupplied ammo during battle...how to you think they keep shooting especially Stug etc...they often have to stay hidden so they are not knocked out and what better way to get ammo then to "teamsay" I need ammo at D4 etc...that way you dont pull out of cover and get knocked out....