[dragonelite]

Either make french or german the language of diplomacy wouldn't be the first time in history that was done.

[Tsiklon]

Proposing either of those two as a lingua franca (irony aside), would be a sure fire way to start an enormous argument in the EU.

Surprisingly with the UK out of the EU; English is perhaps best placed to fill this role, as it is now a "neutral" language, with only the Irish and Maltese contingents who, broadly speaking, don't wield the same influence as France and Germany.

[Rick1]

Legally it could be done, but not practically since English is the language we actually use to communicate.

[GoblinSlayer]

Greek is the most iconic european language.