Speaking of aircraft carriers and zeppelins, the raid did happen!
I think that you could make a 'Special Missions'/'Challenge' category. These are basically real, somewhat obscure achievements done by aircraft in World War 1. You unlock them by progressing the date. Also, https://en.wikipedia.org/wiki/Le_Prieur_rocket
Yeah there's some stuff in the early design stage at the moment around procedural missions, campaigns, etc. I'm also thinking that the short missions might change as the date progresses, i.e. fly the big battle in 1915 and you'll be up against early war fighters, but fly it again in 1918 and you'll be facing late war fighters. I'd probably have an override too so that you could choose the date that you want to fly a mission, up to your current date, this way you could go back and fly against older aircraft. You should check out the discord server, I do almost daily updates and discuss ideas: https://discord.gg/UXnD7Q4UJ4
Okay strange, one of these might help: Discord Support or How to Fix Email Is Already Registered on Discord