I've just seen the game's update presentation and got inspired.
Mathias answered my question if the new buoys can be modded for use on aircraft unfortunately with a; Nope.
But with the new "sound/horn here" waypoint I see a nice option to include sound on the emergency vehicles. I really don't like the vehicles that constantly sounding their sirens, but with this new coming feature I see that issue can be solved.
Only I don't have proper sound editing tools and also only a few sound effects at hand. If someone can provide short useable sound files I may include in my mods please let me know
I'm not sure to what extend different countries use different sirens for the various services, but surely, with help, that can be explained