the general play is pretty solid, i wouldn't mess with it much. more tracks or a triathlon style event with a race, some pve content then another lap could also be fun. basically do one part of a race, hop off. kill x number of things then place orb in gate to open up the next part of the track and finish. this could be made more challenging by color coding the enemies to your player. if 3 players show up and there are six reaver captains each player will have to kill 2 of his marking. the other 4 would be for the other two players etc.