There is only one solution to these problems - Chinese Mandarin, it is the most widely used language in the world.
I vote for Esperanto : no jealous...
Some companies use "surprising" languages sometimes : pilots from a Quebec company speak English or French, some "French" pilots (with a French national company's calsign) speak English, some "N" registrated speak French... depending on the crew's nationality, of course.
When it happens, we write a big "
GB" or
"F" on the strip.
This procedure won't be possible anymore when we change to e-stripping...
Just wait for it.