Greg Savage explains the conflicts, both with scheduling and fighter prioritization:
WEC has guaranteed Versus Network eight events this year. Two still need main events. One headliner should be a 135-pound title fight between the winner of Miguel Torres vs. Brian Bowles and the winner of Joseph Benavidez vs. Dominick Cruz. Brown’s next defense and lightweight champion Jamie Varner’s return should round out the schedule, but it’s a matter of fitting the pieces of the puzzle together.
A Jamie Varner-Donald Cerrone rematch for the lightweight strap is one roadblock to Brown-Aldo happening in September. Varner’s availability is still not known for the late summer date, but if he is ready to go, it would be very unfair to everyone involved -- Varner, Cerrone and the fans -- if the lightweight fight wasn’t made.
Another potential barrier to a Brown-Aldo title fight could come from within Aldo’s camp. Wagnney Fabiano is higher ranked than Aldo, his younger teammate, in most polls and could find himself blocked if Aldo were to snatch the title away from Brown.
I'm not so sure you can't double dip with two title fights on one night, although the television scheduling of that can get dicey if both fights go into championships rounds or a decision. Savage suggests skipping the fight altogether with Aldo dropping to 135lbs and eventually taking on Miguel Torres. That wouldn't be my first choice as the WEC featherweight division is really starting to grow some teeth, but given the constraints of the situation it may be all they have.