One of the big factors in wartime, that simply cannot be accurately reproduced in the historical recreations arenas, is the element of surprise.
We've often read where pilots were called to alert while shaving, eating breakfast.. who knows what else, jumped into their planes and roared off to face the enemy.
Hopefully, with the advent of Combat Tour and the introduction of Artificial Intelligence ( AI ), we can see the following added to the features of AH.
A special events arena is sitting out there with one of the theatre of combats running ( SOPAC, WEURO, EEURO, MED, AFRICA.. ) and the AI has been programmed to strike some target. Be it a mass of B17/B24s crossing the channel from England, G4Ms hitting Henderson Field... etc.
An alert broadcast goes out to all other arenas calling for a scramble. Pilots immediatly log out and report to the arena ( perhaps a flashing bar on the arena selection screen ? ) and read a quick MOTD describing the raid and defense. Pilots check the missions available menu and select their assignment.
Launches are then performed as necessary and play continues as a single life special event.
After the raid is completed, the arena is reset, similar to a 'victory' in the MA and the next surprise is programmed in.
Yes, this is similar to the canned missions we're used to in box games, even in AW, but with the element of being a multi-player environment and you just don't know what to expect.
Now, one of the biggest gripes you're going to get are those that are never online when one of the alerts happen. That will have to be a fact of life, for if you introduce any sort of schedule, you've blown the element of surprise.
Another potential issue will be volume and load of x number of pilots attempting to log out of one arena and into another.
Also, the restriction of having to be in a mission would be a new feature ( which has been 'wished' for in other requests )
Some other possibilities would be having the arena send out e-mails at the time of the alert.
Then you could also use this with pre-registered special events.
Any number of possibilities.