We are 4 players and I am currently planning a 2 vs 2 format here, which I started to call “Hidden Agenda Missions”. I believe it can be modified to a 2 vs 1 “3 player format” as well. Please note, though, that 2 players would be allied and play one list together. So if you were looking for a 1 vs 1 vs 1, the following is not for you:
2 vs 1 Hidden Agendas
I won’t repeat the “Hidden Agenda Mission” rules, please read up on them here.
To be 2 vs 1, you could modify it, in that one person prepares a 10 units with 2 heroes force, while the other two prepare a 5 unit with 1 hero force each.
The single player has an advantage, because they play alone and because some agendas like “be the first ally to…” are trivial for them. So we would need to think of ways to balance this out. Having the player take two agendas would be an obvious choice, if we restrict those agendas to non-trivial ones like Gatecrasher, Reserved, Coward and the like.
I am still fleshing out “Hidden Agenda Missions” and will add more agendas than the currently available. Please let me know, if a 2 vs 1 format would be interesting to your group, and I will keep it in mind while designing my 2 vs 2.