How would you end it?

[JonBeowulf]

I like bringing weirdness into games where weirdness belongs, so I'd go with something like #3 but have the fight be the player's PC and the team at the bridge with the big bad on the other side... except the BBEG and everyone else are poorly-made and blocky constructs with just basic attack abilities (let the other players run them). Rotate as necessary based on who chose the wrong pool.

Not really a dangerous fight, but resources are probably depleted and it'd be freaking weird.