long, long time lurker, loving crazys mod, and finally peeking my head out to post an idea (and hopefully put up some packs soon)
I think I know why gang stuff has been left to basically simmer so long. Their just kinda... there. You have no investment in them, no real way to develop them, or reason to care about them aside from "Goddamnit, I got raided and half my girls are dirty/dead now" "I just lost half my turf, wtf!!" or "Wont they hurry up and get me more girls/territory/money"...
Why not hack up up/modify girlsx files to make gangsx files? Thered still be your standard rGangs, but you could also recruit, say, Homra, the Dai Gurren Brigade, each of the 13 Court Guard squads...
Then, just add a new room to each building call it the Back Room or something, its where your gangs work out of, and co-ordinate with your girls. Every gang you have guarding gives you one guard slot for a girl in the general tab, same for security slots, and catacomb explorers but in reverse. A few girl specific jobs like "medic" (patches up gang members potions cant save) and "gang whore" (self explanatory I'd think, maybe assignable to a specific gang to do targeted morale raising of a powerful gang or keep from losing one that got thrashed last turn) "Recruiter" to add some sex apeall and maybe recruit more members to low gangs.
That opens up a few more gang specific jobs too. Have a gang with crazy good charisma and looks? Assign them to the studio to work as extras, or add security guards to the studio to keep your promoter, or movie shipments from getting attacked. Hospital? Launder prescriptions, harvest organs refine drugs to narcotics, run ambulances (good morality gangs find people and need and help them, evil gangs
make patients). Arena? Bookies (high int is good) beast control (without this, the girl just may find herself being killed by or mated with the beast that beat her right there in the arena sand) combat squad (v.s. girls could get you the spectacle of a challenger getting 'banged in' after being beaten, the chauvinistic power-trip of a girl being "put in her place" or the dark spectacle of one being killed depending on the gang you assign; v.s. other gangs for small unit combat) Farm? Supervise labor (keep the slaves in line) Breed fighting beasts (creates more items like guard dogs to assign to gangs/girls) Grow Narcotics. Cook Drugs. Distill Moonshine. Smuggle goods.
Gangs treated more like girls also frees up a home for the gratuitous amount of gear you tend to end up with a few good catacomb exploring girls once they level up a few times. One girl is easy to equip, but 15 guys?
Added investment for when a girl the player character knocks up has a boy. He grows up and goes to a gang. Gang specific traits like "Bosses [different variants for different positive or negative effects, anywhere from the fruit of your looms being an insurmountable bad-ass that shoots to running the gang, to a failure and an embarrassment you hope gets killed quick]
For girls, well, gang related traits "[gangname] member" - Jumped in or banged in, she wears [gangname]s colors, and they count her as her own.
"[gangname] leader" - in the [gangname] she calls the shots, and they call her boss
"[gangname] mom" - so many of the boys
are her kids, all of them just call her mom
"[gangname] mascot" - she found some way to worm her way into their blackened hearts, now they'll kill anyone who so much as looks at her wrong
"[gangname] queen" (princess/queen only) - (same as gang mom but with royal terminology)
Girls joining gangs, a cross between the housing equation (the more she has in common with them, the faster they want her as one of their own), each job assigned with the gang adding a variable tick to a tracker until you get an event like a customer who cant pay. "The [gangname] all shuffle into your office after their job for the day is done, and the leader steps forward "Sir, we wanted to talk to you about [girlname]. We've been working with her for a while now, and well, she fights with us, bleeds with us, parties with us, hell, she cries for us when one of the boys ends up dead. We, we wanted permission to make it official, sir." - you can choose 'jump her in' (test girls combat skill against gangs, anywhere from girl dies to girl puts the whole bunch in the hospital and is the new leader) 'bang her in' (test girls sex skills, throw a few images and scripts up, anywhere from them losing interest, to her having a gang baby) 'ask [girlname] (she decides whether she wants in or not, and how she wants in) and 'up to you boys (they pick, or ask what she wants). This would also cross with the growing morality system, and allow for some traits to show how rooted in good/evil/stuck in the gray in-between a gang/girl are. A girl that is a paragon of virtue and justice could turn a kinda mean bunch of hooligans to be just like her over enough time. Or a naive young girl ends up totally corrupted by the worst of the worst; put either end of the spectrum together, and prepare to lose one or the other, one way or another. Pair up like moralities for a girl ending up part of a gang in record time.
The gang tab? thats where you assign your gangs their jobs.
Add a Gang Management tab by building management, there you choose your gangs rules, and buy nets/potions like you do anti-preg.
-Girls join gang on:
+With your permission (default, goes to the event chain I have above)
+Jumped in when she earns it (after enough combat missions)
+Banged in if shes worth it (gang generates enough lust for the girl)
+Jumped in if she's going to fight with them (on first shared combat job)
+Banged in when you giver her to them (on first shared/assigned sex job)
+Never (minus gang morale/happiness)
Sorry about the wall of text, heh

I was really, REALLY bored at work today... Hope the ideas help