The title says it all. There are identical weapons platforms present in every military group's armory.
The turret systems are identical between every "car" class vehicle. The turret system for OPFOR's light APC appears to be a continuation from the same manufacturer as the platforms are stored in an aesthetically identical housing as the turrets attached to the "car" class vehicles.
Making matters worse, BLUFOR's heavy APC also holds the identical weapons platform the Marid uses, with the exception of a possible higher firing rate. In the past Arma series such proliferation was not observed, allowing the possibility that these are not the "final" models. Needless to say, lack of transparency on BiS' part concerning future plans makes me feel the need for addressing these issues.
AT/AA specialist weapons platforms are identical. The TITAN system is currently in use with every faction, and I am again unsure whether this is planned for change in the near future. Unguided missile systems are currently different among the factions, but the lack of information concerning future plans has (again) made me feel the need to issue this ticket.
Diver's currently use identical vehicles (save for camo patterns) and primary weapons (SDAR).
I am not sure whether this is even an issue at all, as I recognize that underwater warfare is probably a "frontier" similar to how aerial combat was in the turn of the 20th century, and thusly the technology could very well be in it's infancy (as the SDAR might even be the only UW rifle on the market in this 2035 future-verse). That being said, I address the issue simply because of the observance of identical objects in use.
UPDATE: Since the last writing, this problem has only gotten worse. Duplication methods have reared their ugly heads with mobile artillery and AA units, as well as entire duplicated vehicles in regards to UAVs/UGVs. All static weaponry is virtually indistinguishable from another, save for a few who retain their respective faction's camouflage patterns. Still no public confirmations from BiS on whether these are placeholder items, but the fact that they are present in the "release candidate" on the dev branch suggests this is indeed final product.