I was thinking that the support class should be able to place down with squad points at a limit of 1 per squad a stationary .50 cal (I think 1000 or 1500 squad points would be fair)
Actually add iron sights to it of course not whatever is on the Humvees
I think you should be able to reload it at the cost of a support consuming one of their ammo boxes
The right and left directional turning limits are what would be demonstrated by my badly drawn 3rd picture so the main counter to the emplacement would be getting close or pulling a wide flank or of course using a vehicle or rpg to take out the emplacement
I would want the support to be able to pick up and move the emplacement when they wanted to change their position but I'd understand for game balance if you had to unbuild it and respend squad points to place it elsewhere
You should not be able to destroy the emplacement by shooting at it with any small arms you should have to use explosives (excluding grenades) so c4, rpg, lav, tank
I think this would be a fun feature and as long as it was implemented correctly it would be fair