It should probably be possible (if not necessarily easy) to go the entire game without setting foot in the catacombs.
That's doable at the minute. It's not particularly easy, thanks to initial costs and trying to make those back(I don't do 'bad stuff' like kipnapping by default, nor randoms when I play with 'above-ground' girls. I'm glad that random monster pack was made...there's too few random models, which turns me off from having them in general. Attack of the clones, you know? Maybe I should turn some of the custom girls into randoms to ease the issue. At least then they'd be clones I'd want to see...).
So, arguably, it shouldn't be possible to do that. Well, not be possible to withhold most of your gangs until they're fully trained and equipped.
Now, the issue in this case is if you want your gangs to live, they have to train-they are practically useless except at max. They just take too many casualties before that point, and will eat your potions like water, even on guard(you really are under constant assault after the initial wait time)...for ZERO benefit to them; they gain nothing from working other than casualties.
If they were gaining power from doing jobs, I wouldn't keep them all in the training camps till they were mini-gods. Even the weapon upgrades aren't as effective as the training-or at least it doesn't feel so. There's a case to be made that you don't 'need' training if you have potions under the current system, but I find that's not the case.
I wonder how fast you can beat the game currently? Sabotage can bring in a hell of a lot of money...
EDIT-Answer: fairly quickly and safely, even with 6 untrained gangs(And one guarding, one training), sabotaging from the off. Income is high enough that it can pay for itself and make significant profit even if they screw up and can't attack a few times. Roughly 30 or so turns(wasn't keeping a proper count). Perhaps that shouldn't be possible. Then again, the rivals start off with fairly large operations to begin with, and if you wait, they can take ages to kill off even now with invincible gangs because they're so vast. I'll try without weapon upgrades, perhaps. See if it takes longer.
EDIT2:Wow. I guess it's just luck that decides it, because this one was about 15 turns.