I understand from testing of the current (then brand new) Mercedes G-Wagon with a .50 cal on the roof turret resulted in cracked sheet metal. Our patrol variants did only mount the C6 GPMG during my time.

I figure someone had HUMVEE 50 cal envy and wanted to see what would fit.

The current HUMVEE makes a decent gun truck, (although crap to ride in) the Merc G-wagon, not so much, it's more of a nice Tim Hortons coffee runner in my experience.