You'd need a language that doesn't rely on accent marks or pictograms for sure (unless they have a very tiny set of characters), and that probably eliminates a lot of languages.
Some languages have an official mapping, like in German where you can usually replace ä with ae, ü with ue, and so on.
Otherwise the accent could be a separate character, as in cafe’. Probably would be acceptable for this application.
You'd need a language that doesn't rely on accent marks or pictograms for sure (unless they have a very tiny set of characters), and that probably eliminates a lot of languages.