I would love to have a way to play this with friends or other enthusiasts online. I have skimmed the rest of the forum and haven't seen this suggestion which I think would be relatively easy to implement.
The game is turn based and already has a prompt for new human player. There is already a way to save games for later play as .gam files. To make this easily playable online via email seems like a pretty good option... I mean I wouldn't want to wait while the other guy takes 5 or more minutes on a turn later in the game anyhow.
I am not a programmer but I have worked in the software industry and I will describe what I envision would need to be done here.
At the beginning of the game collect player names and emails. Prompt for changes to piece attributes now because dialog will be locked later.
Save the game at the next human player prompt, and open the computer's default email program with the saved file attached and preaddressed to the next player. Alternatively send directly from program, but still use regular email accounts and file attachment so that you don't need to provide a server or have people mess with firewall settings. If either of above is impractical, just put the file on the clipboard and let the users figure out how to send.
Either shut game down, or otherwise put in standby until called for next turn.
Add password input to next human player prompt. First turn of game have player set their own password in a standard change password dialog box. After the first password input, the player would be need to know the password in order to change it...
If necessary (may be the demo/licensed double install on my machine) modify the way the exe handles double click on .gam files and opens directly to game and turn as required.
If necessary include piece attributes in .gam files (probably there already).
And finally... don't kill yourself encrypting the passwords or trying to enforce that people have not played a turn more than once in order to get better outcomes from a turn (i.e. cheat). That stuff can more or less be a matter of honor, I mean it's not like the fate of the world depends on it or anything
As an old SConquest player I love the game,was really excited when I found it and very pleased at your execution, good stuff. But it would a lot of fun to play this with others without having them at the house for hours and hours... not going to happen outside of my old college dorm.
PS... The other big feature for me would be patrol move with specified start/end points (even if I had be at start point to initiate and you didn't provide logic to prevent fuel problems with planes). In fact, I would prefer you remove fuel logic from bombers.