While English is still the de facto lingua franca, with the US burning bridges to Europe like there’s no tomorrow, and the UK having left the EU, should they adopt an easy-to-learn auxillary language?

I’m thinking of an language like Esperanto, but not necessarily that. I was intrigued by Esperanto and went through the course on lernu.net and found it easy to pick up (though I am by no means fluent yet). While it is constructed, it was developed without any modern linguistic knowledge, so another option could be to construct a new language for this purpose, or adopt another already developed language that would serve the purpose better (I don’t have an overview of what is out there).

I know there are several official languages already, but I imagine that leads to a lot of overhead. An auxillary language could make communication easier, and make it easier for citizens of any member state to participate in the Union, and would to some extent remove any power asymmetry resulting from native mastery of a language.

Good idea? Poor idea? Why? Why not?