three down votes with no reasoning, i see we have some trolls.

Or people who disagree.

I downvoted. Here's my reasoning.

"The HEMTT's objective is to provide heavy transport capabilities for supply and re-supply of combat vehicles and weapons systems for the United States Army. It is distinguished by extreme mobility compared to standard 5-ton trucks, thanks to its large number of wheels and turbo-charged engine, combined with all-wheel drive and very large, low-pressure tires. Though far less publicized than the Humvee, it has been extremely important in transporting logistics behind quick-moving forces based on the M1 Abrams tank. Having proved itself as a key workhorse of the US heavy tactical wheeled vehicle fleet, about 13,000 HEMTT vehicles are in service today."

I fail to see why an 'exposed gun' would help the HEMTT meet this objective.

it helps if its convoy gets ambushed and it needs a way to protect itself if the mrap/whatever is down or out of ammo, just like the reason some have them in real life, but it doesnt have to be an exposed gun it could be the same type the mraps have or something along those lines.

Would be one badass HEMTT.

Armed HEMTT is mainly for convoy operations and defend themselves

http://www.military-today.com/trucks/hemtt_l1.jpg

also there is a AA variant of the hemtt

http://www.defence24.pl/uploads/images/2013/08/184605jazgjvi2f9zbwvgw.jpg

Yeah i know, and as far as the Phalanx CIWS version i doubt they will make that version, but im sure a modder will.

Look at the T100 from ACR there we had a transport truck simmilar to the Hemmtt which had a gun to defend itself, makes sense to me.

The integration of an exposed weapon or some form of weaponry into the HMETT holds the promise of augmenting its capabilities for a more versatile and impactful role in military and tactical operations. Nevertheless, careful consideration and adherence to ethical guidelines are paramount to ensure responsible and lawful deployment.
https://en.wikipedia.org/wiki/Heavy_Expanded_Mobility_Tactical_Truck rails