Great, we are already four
I will host a ranked match and send you invitations 10 minutes before the start. By the way, I am on Xbox 360 and I hope I can use my mic (if you are on Xbox one or later).
I think it would be great if deal first with the 4-player achievements ('Restraint... Not' and 'Bum King'), then we can focus on 'Serial Killer' and 'SKX' (who need them) cause they don't require four players and therefore can be done in player matches.
P.S. If you want, we can set up another session earlier this week.