Oh yeah. Once I meet some people down in LA (I just moved down here), I plan on running a Nu!Boba Firespray with an Imperial squadron. Because Nu!Boba is awesome.
That doesn't seem fair to the S&V faction folks. Otherwise, I'd run the nuHWK and nuY-Wing with salvaged astromechs and illicit upgrades with my Rebels. And in the end you don't have so much a third faction as an aces pack for Rebels and Imperials.
And on the flipside, it's not really fair to the rebel players if the Y-wings they've hoped to see upgraded for so long can only be played by the S&V faction.
Scum are certainly their own pilots (and there's a good chance the named ones will be more cost effective than Horton), illicit upgrades, and salvaged astromechs. However, Y-Wings will have likely have access to turrets and astromechs that are in the kit, so it's not like they're just ignoring the Y-wing.