I had some ideas regarding STAG.
Either keep the current STAG skin or make re-textured SNG soldiers and give them red camo or something.
Weaponry:
-AR-55
-The Vector SMG
-The vanilla police pistol
-The assault shotgun
-RPG
-The DLC Grenade launcher
Vehicles:
-N-Forcer
-Specialize Police Cruiser
-Challenger Tank with different paint job
-Vulture w/ new paint job
-Bear APC w/ Paint job
Regarding notoriety:
Level 1 - Attack you with fists and stun guns. Drive white police cruisers with orange tinted windows.
Level 2 - Still use cruisers but use lethal force. Attack you with pistols and assault shotguns
Level 3 - SMGs, Shotguns, and pistols. Less Cruisers and more Humvees and Unarmed Enforcers.
Level 4 - Assault Rifles, Shotguns, the whole deal. APCs, Humvees, Enforcers, and Vultures instead of condors.
Level 5 - Like 4, but with tanks, VTOLs, and rocket launchers. Yes, they have lasers, but I like fighting them. Consider them to be their "special" weapon.
Just my ideas. Hope they inspire you with good ideas.