While having a Scum faction might end up being cool, it just seems to me like it would be the publishers pandering to the popularity vote. Like when the Pirates of the Carribean movies went from being about Will and Elizabeth to being about Jack Sparrow just because people liked him way more. Like way way more. Sometimes what is the popular choice, is not always the right one, nor the one that makes the most sense for the medium.
In the case of Armada, the medium is the stately yet high stakes combat between opposing capitol ships set in the Galactic Civil War. Adding a Scum faction full of ships which in this games rough scale would be comprised of probably 80% flotilla sized craft and under does not seem to fit that medium particularly well.
Not saying it won't happen, because money and popularity, just as in Pirates of the Carribean, will still ultimately win the day. I just don't know if I'll be that happy about it if I see it.
I think that there's plenty of capacity to have a "scum and villainy"-esque faction in the game, without compromising on ship size and quality. The Zann Consortium were a faction in Empire at War, and have a well established fleet of different sized ships that are both unique to them and stolen from both Imperials and Rebels. They have unique examples of ship sizes already in the game (large capital ships, medium-sized frigates, small corvettes, transports and squadrons), all of which could be produced into a fleet. Plus, given that we have the Raider, there is nothing to prevent FFG producing their own.
The idea behind the Zann Consortium was that it was a crime syndicate that eventually incorporated other groups (such as the Hutts), and was therefore a group of power and influence sufficient to rival both Empire and Rebels. I have no doubt that their setup and tactics would be different from those of the Rebels and Imperials, but currently there is little in the game that would prohibit their being involved; none of the missions are faction-specific, and it's easy to see why a large crime organisation might participate in an intel sweep or the taking of a space station.
In X-wing, they already have Starvipers, Kihrax Fighters, M3-As, plus Y-wings and Z-95s. There are your squadrons. Could use existing Villains, possibly with alternate cards. Add to that a Crusader-class corvette, a Vengeance-class frigate, an Interceptor IV frigate, and a Keldabe-class capital ship, and you've got yourself a distinctive, credible and interesting wave. Plenty of commanders already, and could bring in some fun ones from Star Wars Rebels (I'm thinking Hondo).
You could even build in a mercenary system - let's say the Consortium ships tend to be cheaper than their Rebel or Imperial counterparts, you could have it so that they can be incorporated into a Rebel or Imperial fleet as mercenaries, adding a point cost. If they had certain abilities or qualities that neither faction has, this could make them an attractive addition, and not necessarily require you to build an entirely new fleet to use them.
For more details on the Zann Consortium, the Star Wars wiki has loads of information. As I said earlier in the thread, I don't think this would be Wave 4 - more likely wave 5 or 7, one that comes between two film releases. But I think it would be an interesting addition, and a lot of fun.