My 2-cents. Often times the 60mm mortar (or any light mortar British 2", German 50mm) would often be left behind and the crews used just as regular infantry (fill in for loses). Even though I believe the US 60mm mortar was a better light mortar than other equivalent types, I know often it was considered useless. Standard GI mentality. (I don't believe that nor does my buddy in the Marines who hauled one around the Persian Gulf) Now many of the 60mm US Mortars was a part of a SQUAD (Check you AIB TO&E) These boys very easily would leave it behind. Thus just a squad which you can easily say is figured into the force on the board. I accept that, no problem. Besides, if you don't want them lagging around in the rear, have them guard prisoners. There not going to waste there.
As for German MG42's. There 4-6 men "team/crew" was for hauling ammo/spare barrels and yes, close defense. But once the 42 used up it's last round, they would march off as infantry, 98ks and whatever. But they would NOT abandon the weapon. I'm not exactly sure what they would do, but they are not going to leave the single most important item in German squad/platoon/company level tactics behind.
If I use tanker logic (OK stop laughing), and I run out of ammo, I would return to the platoon/company/battalion area and re-load.