A finite number of convoy ships spawn to start ~6 or so for a 2 ship lobby, only these ships can carry cargo.
Rather than start with cargo the convoy steals it from the refineries as they go, up to 2 per refinery after which the refinery becomes a target for them (worth points if they fail to destroy it). To steal cargo they remain there for a short duration as per infiltrate. If you get close enough and there are refineries remaining ahead they skip stealing in favor of continuing to run away.
The convoy ships attempt to leave the map via the far end carrying cargo with them, convoy ships with no cargo remain grouped up as long as there are enough refineries remaining to provide them cargo, otherwise they attempt to turn around and retrieve any cargo left behind by ships you killed.
The match ends when either no convoy ships remain on the map or ~4 have escaped with cargo (in which case you lose), bonus points are scored if only 2, 1 or 0 ships escaped.
Non convoy ships and the boss spawn as usual and attempt to keep you away from the convoy and/or join formation with it as it moves along.
The balloons can just be left behind after killing convoy ships, no need to drag them with you closer to your opponents objectives. Some advantage may be gained by keeping them away from any 'spare' convoy ships with nowhere else to get cargo.
