Option 1) You know swedish planes for Sweden, french for France, German for Germany and so on… like you can just give different camouflages as grindable or for gold, because why not, instead of adding copy paste aircrafts. You know as separate vehicles if there is copy paste but has different wepons.
Option 2) Another option is to give to German TT vehicles from all German speaking countries, but only unique ones.
Gajing won’t add all countries fully to WT ever, so better would be adding only the most important manufacturers, that is why i support korea, turkey and India.
In my opinion simply unique vehicles from Austria and Switzerland would fit well German TT to not spam copy paste vehicles too much.
Important manufacturers make hulls, airframes and turrets, munition used and bought by a lot of countries in world. Cockreil turret (i probably spelled it wrong) is very common as well some other turrets, many vehicles like F-16, MiGs, bmp, Humvee, CV hull, is very common.
I have nothing against modified vehicles, but if you want new independent TT, make sure it has at least half very unique vehicles or highly modified.
Does ground vehicles are more unique than aviation at least? I believe they are for sure, question how much.
I see that austria is producent of Pandur which is quite popular and often bought chassis, equipped by many countries with different turrets. There is tons of demonstrator variants, by not austria but also others.