Give Vix Armed Security Officer+ the option to have a Revolver holster instead of the Glock one. Most common revolvers used by security officers in the US includes: Smith & Wesson Model 10 (or 64/65), Smith & Wesson J-Frames (Model 36/60/360), Ruger GP100, Ruger LCR / LCRx, Colt Detective Special / Night Cobra, Taurus 856 / 66 Combat. Commonly in either .38 or .357
Give Security Commander+ the option to use a .44 chambered revolver.
Give Senior Security Officer+ the ability to equip and store in their vehicles an AR-15 or similar semi-auto only rifle.
Give TRO/Tactical Response Officer the options to carry and store in their vehicles a MP5 or UMP (Or the most popular SMGs used by security: B&T APC9K; SIG Sauer MPX; FN P90; Heckler & Koch MP5 (and variants like MP5K/MP5N); Heckler & Koch MP7) and a tactical/combat shotgun like the Mossberg 590A1, Remington 870 Tactical, Beretta 1301 Tactical & A300 Ultima Patrol, and Benelli M3/M1014 (P.s. just like the revolvers, I searched which shotguns are the most used by security in the US)
Give Armed Response Specialist+ a M4A1 or other form of burst-fire/automatic carbine.
Give vehicles with tactical security response liveries for TRO+.
Give supervisor livery equipped vehicles for Sergeant+
Possibly add a Bodyguard and/or Armed Bodyguard and/or Escort Officer ranks with their own uniforms and vehicles.

This would match both the Senior S. Officer description of them having rifles, and would make sense for TRO/ARS and supervisory roles. It would also expand Vix and give a reason for people to grind after reaching 1500xp/armed security officer since after that you unlock nothing new no matter your rank.