...Uh...or you could just ask that minimum team requirement be reduced, which would likely be much easier to code.
Open Archetype Suggestion thread!, Kirsten's Epic Weapon Pools, Feudal Japan, Etc., Alignment specific Rularuu iTrials!
If Masterminds didn't suck, they'd be the most powerful AT in the game.
I don't see the devs deciding to add a feature that would allow players to turn multi-player content into something that could easily be abused by solo farmers/power-levelers.
I have found it frustrating when I can not find enough players to fulfill TF or trial team/league requirements. I have a solution.
"Temporary Team-Mates"
This could easily be implemented and avail from the store. They would be longer term signature pets which would "Fill" one team slot each. Make them available in 1 hour, 4 hour and, 8 hour duration. Also have 2 or 3 power sets per Archetype avail for "Purchase" so we have a little variety.
Additionally there could be a 'Hero-for-Hire" office in 2 of the cities on hero side and a Villian-for-Hire office in the Rogue isles on 2 of the islands. Allow for a "Straw Boss" Day job badge that will allow a player who logs out 21 days in a row at the labor hall to receive one free 8 hour "Temporary Teammate" token redeamable in the store.