We've already seen Luthier changing aircraft mid-mission in one of the videos. We also know there will be some sort of MDS functionality (AI units in dogfight servers).
Combine the two and you have the solution for the scale problem between the speeds and travel times of aircraft and ground units:
Before logging off the server for the night, set up your mission for the next day by specifying a set of AI controlled units to spawn and move along certain waypoints at a certain time. Next evening you join the server and select one of these AI controlled units to spawn into and take control of.
Voila, you can now simulate a sortie to Berlin on a 1:1 scale map without having to spend a full 6 hours in front of your PC, as well as conduct a combined tank/infantry assault without having to drive all the way to the front. The AI does the navigating for you, you jump in and take control a few minutes before the action starts. Add an ownership flag or a password for the AI units (so that each person can have a choice of his own reserved units to spawn into) and you're good to go.
I don't expect the ground combat part to be as hi-fi as the flight part, just like an ArmA player doesn't expect high quality flight models in what's predominantly a ground combat sim. Sure, when driving panzers in a future expansion of CoD i'm sure the ground textures will seem blurry in comparison to viewing them from the air, but the aim in such a case is to simulate an entire scenario with emphasis on one part, rather than a choice between doing it all perfect or not at all.
I don't care much for ground combat in CoD but it would be nice to have in the future for people with more diverse tastes. However, what i'm very interested in is some sort of mechanic like the one i described to facilitate long range bombing campaigns in an online setting.
Small flying distances and scaled down maps for the sake of playability are one of the top reasons we fly in an unrealistic manner. In reality you don't take unnecessary risks when you have a 500 mile run through hostile airspace before you reach the nearest friendly base, but in IL2 we're usually withing gliding distance of the home base or at the very least friendly lines.
And let's not even get started on the payload considerations, we load up on 25% fuel and optimize for combat performance in a way which was impossible to do in real life for strategic level actions (and even some tactical ones), because we wouldn't even be half-way to the combat area before running out of fuel. We currently have aircraft with thousands of miles of range on a full tank, being flown like go-carts or dragster hot-rods with 25% fuel or less because the small size of the maps permits this.
This takes away a huge chunk of tactical decision making, both in regards to mission profiles flown as well as to how reckless we can be. It's an understandable compromise for the sake of playability, or at least it has been up till now.
However, if there's a way to make other compromises for an overall more realistic picture i'm all for it. I'd prefer having realistic map sizes, payload and tactical considerations at the cost of unrealistically spawning in my bomber just outside the coast of the Netherlands, rather than fly the entire sortie on a 1:3 scaled map with a bomber on a light fuel load that's performing way better than the real ones did in similar missions.