Thanks for the comments!
@ midgardsormr, the only problem I'm seeing is that no one likes the Trajev so they wouldn't want to use their language; in fact, most countries think the Trajev disappeared years ago. The reason no one likes them is because they started gathering knowledge during a very violent time, and when a major catastrophe left a gaping crater in the northern rainforest, everyone assumed the Trajev had helped the man responsible by providing the knowledge he needed. But the Trajev do still collect information, they just pretend they're merchants/mercenaries/&c. - anything that allows them to travel.

Other than that, however, I'm liking the idea of a "lingua franca" a lot - I can also re-label maps with names in the local/national language when I develop them ^.^ Thanks again.