Please use JPEG for that map image, 60% to 80% compression ratio. The image you've posted is quite small yet has 300kB filesize! I suspect it's PNG, which doesn't compress natural details at all well. Also, PNG is not currently supported by Game Hunter.
Other Collaborative LevelsOnly one I see played at all is
Army Base. They objectives are technically very simple. The difficulty level is made extremely high because the AI has endless swarms of National Guard and several tank guards.
Teamwork is an absolute necessity. It's fascinating (to me, at least) how each player takes on the same scenarios in a different way.
Unbalanced Team GamesDeCon Labs again has technically very simple objectives but it's a one-against-all team game. The bigger team has to play co-operatively and very tactically to win. You could program bots to play it but they just don't have the skill. You'd have to give them Electro Gun or just add dozens of them for it to be a challenge.
Cops & RobbersThis is a mode is I bet we all dream about! I'd make the host the criminal and all other players are law enforcement. Natural law enforcement would also be present and would only attack the host.
Trouble is, coming up with missions which take a few minutes but include loads of action. They also have to be repeatable. And, ideally, somewhat randomised.