I've been playing with the idea on how the borg would be a playable faction, then it hit me.
Borg Empire - when janeway "destroyed" the collective, many factions form out of the chaos, only one survived the collective's attempts to restore order to itself. They use borg ships but operate like a combination of the Federation and Klingons, conquering worlds by sending 50 ships at a time to gain a foothold then attacking another as the defenses are spread out, as well as developing radically new technologies to improve themselves. This is the main reason that the collective is acting so aggressive, believing the Undine to play a major role in the re-assimilation of the Borg Empire. They do assimilate species but mainly for use as crew and soldiers.
The ranks are basically the player's level, a LC 4 would be 1.4. Their crafting focuses on plasma weapons (or antiproton if the Romulans are given that). Their territory is deep in the beta quadrant, far to the right of Klingon space. Exploration mission wise, they're focused on combat, scanning, deploying equipment and abduction missions (*******ized versions of hostage rescuing). They have a transwarp gate and can access the high level borg mission for Collective vs Borg Empire action.
All borg ships have universal Boff slots and large crew numbers
Probe - think BoP with sub-system target
Diamond - fed escort that has a bonus to turrets
Sphere - cruiser
Cube - Heavy Battle cruiser, turns like the carrier but has a cutting beam ability that acts like a "hull steal"