New game modes would be interesting. The Star Wars LCG has a box designed around multiplayer, with a special deck designed to go against 2-3 opponents at a time. I’m not sure it’s hit the sales figures that would make FFG consider porting the idea into Netrunner, but I’d certainly like to take a crack at playing a suped up megacorp against a pair of runners.
Maybe based around another joint effort like the Chronos Protocol storyline? Or multiple small Weyland Consortium decks that represent members of the consortium? On the runner side, maybe revive the Collective with a specialized deck that can easily threaten multiple servers in a turn, but only in bursts?