THIS MOD WILL AFFECT THE GAME'S DIFFICULTY, USE AT YOUR OWN RISK
PAYDAY 2's spawngroups are...functional-ish, they do their jobs well enough, you have two regular enemy spawngroups, one for shotguns, one for rifles, and two for flanking variations of those types, three types of shield-based spawns, two tasers for charge and flank, and a bulldozer and cloaker spawngroup just to spawn those units.
However, they used to be a lot more varied, and complex, at times, even ALARMINGLY DIFFICULT to deal with, before Hoxton's Complete Anti-Fun Update Housewarming Party, cloakers and tasers paired up together, dozers were occasionally covered by shields, FBI Veterans and HRTs spiced in with the normal units, and you'd see UMP Gensec enemies on DW alongside your usual enemy types...I missed that, so I brought it back...but with a well-deserved modern touch-up.
Rather than attempting to completely restore the previous functionality of the old spawngroups, which isn't really possible without breaking the spawns, I decided to opt for working with the current game's spawngroups and letting them do their intended jobs appropriately, while restoring the enemy variety and some of the pair-ups that could happen before-hand, and even adding a few entirely new ones!
This mod works online, even if you were to host pubs, meaning people that don't have the mod will still see the many different enemies that spawn.
Notable features and enemy spawn changes:
-Re-added the HRT and FBI Veteran-type enemies, FBI Veterans deal 75 damage on DW, more than the heavy tans, so watch out for that!
-Almost all special enemy spawn compositions and some normal flanking-type enemy spawns have been drastically altered to be more tacticool/effective. (It gets pretty mean on DW/DS, enjoy that occasional heist-ending dozer/taser combo on your taser-charge spawns. :^) )
-Reduced heavy Tan spam.
-Rifle units have a 1/3 chance to be replaced by an SMG unit on Overkill, Mayhem and DW, the same goes for units spawned in Boiling Point and Cursed Kill Room.
-Made the Skulldozer spawn naturally on Mayhem to create an even scale of dozer-types being added past Very Hard.
-Made Gensec Shotgunners spawn on DS for consistency with other difficulties' spawns. (There are no ZEAL Shotgunners, sadly, but, y'know, Forze Z is a pretty specialized task force for last-resort situations, and Gensec IS private security, I don't doubt even the government hires them for purposes that the government didn't really plan for at times.)
-Slightly tweaked some stuff related to fade-end time, max enemy spawn caps, special enemy spawncaps and such, so that the overall number of enemies and specials that an be active at once don't struggle to spawn.