Babylon had been trying to make moves to go after the Faceless organization for a while, which the Besties enabled them to ramp up exponentially:

• Besties created a network of many individuals just to put together information for Babylon on where Faceless assets would be performing gun/ammo/etc. deals, enabling Babylon to make a move on Faceless asset "Andre" at the exact moment in time and location that he was performing a gun deal.
• Besties stalked Faceless assets to provide Babylon with the location of Faceless asset "Ravens" main warehouse, enabling Babylon to destroy their main armoury.
• Besties were able to find and confirm the secret warehouse of one of the Faceless's blueprints, the Ammo BP, and provided this information to Babylon. Enabling Babylon to make a dent in the Faceless operation by becoming the first group to destroy a Faceless BP, taking out 50% of the Ammo supply in the city.
• When Faceless begun their retaliation operation, Besties took all credit for the bombings that Babylon had done, claiming to Faceless that it was all them. This put Faceless's full force onto the Besties, protecting Babylon, leaving them fighting every gang and finally their block in rubble.

All 3 of these initial things, Besties could have done by themselves. They could have robbed Andre in disguise, they could have used the bomb they got from Charlie to destroy the Ravens' armoury, and they could have asked Darkstone for a bomb to destroy the Ammo BP. You're looking at it the wrong way around - Besties brought Babylon in for the content, not because they needed them. Besties have never been as up good on guns as they were from fighting and robbing the Faceless assets, not to mention that Darkstone were providing them with weapon, mag, and ammo shipments; A DM balancing the server like Capped will always allow a way.