I think that some changes and additions to movecraft sound effects would be a neat update and would make movecraft more fun.
1. A horn for Zeppelins and warships. Could be used for signals, warnings, or greetings. This horn would be heard from far away. There would be a cooldown for it so that it couldn't be spammed. A potential command could be /horn.
2. Reload sound effects. With tanks, and ships, you can KIND of hear the shell being rammed into the breech, however it's kinda subtle, and only shows when the loading process BEGINS. I think it'd be neat for there to be a kind of reload sound, similar to that of reloading in World of Warships or World of tanks as an indicator that the cannon is ready to fire. This sound would be like the radar ping sound, in that it's not directional and can be heard from anywhere on the vehicle.
3. Shells that are passing by should make noise. They have a pretty notable sound that they make IRL and in many games that is absent from CCNet.
4. I know the server is supposed to be set in a kind of early 1900s setting, however everyone already models planes after fighter jets, and fighters even have afterburners, so I think a sonic boom for fighters going into afterburners that is about as loud as a 14 inch shell detonation would be a neat addition.
5. Fighter machine gun sounds just don't make any sense. They sound like something that has a much higher rate of fire than fighter guns actually do. I'd like to suggest a more realistic sound effect that is actually proportional to the rate of fire of the fighter machine gun.
6. Getting hit by explosions and/or shells should make sounds of metal or wood banging/tearing as a better indicator of being hit.
7. When a vehicle is destroyed, a very loud explosion should be made as it is more realistic and simply kinda cool.
8. There should also be a kind of "reward" sound for sinking someone, kind of like what is used in World of Warships or World of Tanks. Something similar to landing successful cannon shots on your enemies would also be a neat addition; however, I see how that may be utilized in combat.
9. Tanks and trucks should have idling engine sounds.

These suggestions are those I could think of while writing this and I'm sure there are many more that would be interesting to add. There could even be a toggling menu for these sounds if they are implemented.