Personally I'd like to see some mutant waves
Shadowcat (blue costume)/Meggan
AOA Colossus/AOA Shadowcat
and a pure redhead pack
Jim Lee Jean Grey and Mary Jane Watson Parker
Good start, but is there really that much love for Tabitha? Pair Siryn with the already teased Warpath, with his red/black X-Force variants.
As much as I want Meggan to go with Cap (and expand the Excalibur team!), I can see blue Kitty and Magik making a better pair, so that opens up the Blink 2pk for MIMIC (with reg and 'metal' arms, possibly detachable wings?). I'd also want to see Husk get some swappable limbs, too, showing off her power.
Namora/Morph - AoA/Exiles variants
Heather "Sasquatch" Hudson/Beak or Sheriff Jen "Hulk" Walters
Power Pack: vary the power switched costumes? or 2x 3pks?
AoA Nate Grey/Essex (Sinister)
Aesir (and an Olympic set):
Odin/Thor (current) - "Thorcules" #132 variant head?
Neutron/Starbolt - black Colossus and another "Human Torch"!!!
CLASSIC Squadron Supreme:
Hyperion/Power Princess - var. King Hyperion (Exiles)
Nighthawk/Whizzer - NH2 var (black/blue)
(Blue Eagle/Lady Lark)