Update: It looks like you can run 3Y, 3Z, 2 hwk, 2 fire spray. Thanks to a couple of guys on the UK X-Wing Facebook group (link to the right 😉 )
Fantasy Flight Games have just updated the official tournament rules (27/02/2015) to make provision for the release of Scum and Villainy.
The main rule that has changes is to take account of non-scum dials and ships:
Multiple Faction Ships
All pilot cards and ship tokens in a player’s squad must belong to the same faction. If a player’s ship has different versions in more than one faction, he or she may use any version of that ship’s model and dial in his or her squad.
Multiple Ship Example: Scott is fielding a Scum & Villainy squad consisting of four Z-95 Headhunters and one Firespray. His Firespray model and dial are from the Imperial Firespray expansion, two of his Z-95 Headhunter models and dials are from the Rebel Z-95 expansion, and the final two of his Z-95 Headhunter models and dials are from the Scum & Villainy Most Wanted expansion. However, all of his pilot cards and ship tokens are from the Scum & Villainy faction.
So this means that you can use your models and dials for your Firesprays, Headhunters, HWKs and Y-Wings but you have to make sure that you have the base cards and pilot cards from the Most Wanted box.
I’ve not had a chance to open my most wanted box yet so I’m not entirely sure how many extra’s you can run with this yet, but will update the post when I do open it and figure it out.
This was an unexpected update from FFG and a welcome one as it lets you ease into playing the Scum and Villainy faction.