I would like to see them add in a power that ties your Primary set and Secondary set together. It may be possible that they could do with through the the new Incarnate system. Alot of this would take to long to make and would most likely never happen but here are some ideas
Some Examples all have long recharges
Fire + Storm = Inferno Tornado - High Fire damage/ Medium Smashing Damage over time Chance to leave burn on the feild
Fire + Force Field = Holds group in FF and Burns him
Earth + Storm = Volcanic Tornado High Fire damage/ Medium Smashing Damage over time Chance of Hold (Volcanic rock)
Earth + Force Field = Holds group in FF and fills up with Toxic gasses
Ice + Storm = Blizzard Tornado High Ice damage/ Medium Smashing Damage over time Slow chance for Hold(Ice)
Ice + Force Field = Holds group in FF and freeze them
Illusion + Storm = a Torando made up of Ghost High Psi damage/ Medium Smashing Damage over time
Mind + Storm = Massive Psionic Lighting Strike that confuses everyone.
Electric + Storm = Massive Lighting Strike across the field from many clouds
for Masterminds they can combined/Sacrifice their pets into one super powerful elemental pet that would represent your secondary power for a sort while.
etc...What power combos would you like to see?