I'm a big fan of the 40k universe, and I know my fair share though I don't know about Gorka Morka speciffically :/ Sorry. As for the questions,
1. I like the idea of us each playing our own gang, because there are so many options for turf wars, especially on something the scale of a Hive. Bloody combat through the levels, from the spire to the underhive, I love all of it.
2. If we're controlling our own gangs, then I think use of non-ork mobs is really up to each player individually, since each gang will have its own traits that make it unique.
3. As long as I can play an ork leader wearing a pirate hat waving around a chain cutlass? i'm all for this! :D
Edit: Well, now that I have a better grasp on Gorkamorka, I'm still fully in favor of this role play, though please disregard everything said in answers one and two >.>