[Safe-Keeper]

1, Co-oP is an option ( you and team mates taking on the enemy )
2, side Vs side ie:- ( Us Vs IJN ) you get to choose what side you want to be on

That'd pretty much be a given, I think. Free-for-all and World Wars don't go well together.

There'd need to be some balancing involved, though. Although I never really played World War II On-Line (only the off-line demo), I hear one of the worst issues with it is that you can change teams at will. So once one side starts to really win, everyone defects to that team.

They'd need to implement something that kept players from joining an overwhelmingly winning team, or switch sides once they'd joined a team.

3, The WHOLE map used after all WWII was a WORLD WAR so you should be able to fight in any Theatres
4, You get to choose what you want to use ie:- player controlled MTB's, Subs, planes or what ever.

Those I'm less sure of.

Creating the entire world would take ages, even with a big team and lots of time and resources, and I'd be happy with only one theatre. But I suppose they could for example do the Pacfic first, and then add the Atlantic with its forces with an expansion pack (I suppose the Surface Ship Command-part would have to be an expansion-pack, too)?

As for letting the players fly planes, Silent Hunter and Destroyer Command are ship/u-boat simulators, not flight simulators, so that one sounds fishy to me. Having said that, I'm sure it'd be fun to take off from Midway in a Catalina packed with depth charges and gun ammunition and go hunt Japanese subs with it!

And maybe if you commanded an aircraft carrier, you could be given indirect command of the planes stationed on your ship? Kind of like the way you can command fleets of destroyers in Silent Hunter IV? I'd like to command a medium cruiser and be able to deploy my ship's sea-planes for some short-range reconnaissance.

My selection was option 3. I could care less about the frag-and-splash world of multiplay, regardless of how massively online it is.

Multi-player can be very complex and realistic, actually. Case of point: World War II On-Line. Download the demo and see if you can even start a Jeep.