For the matters of "your" consistency: Will you make your characters then also speak Ylian only (or whatever), instead of english?
You're muddling two fundamentally
different things as one. Art is hard-coded visually. It is what is understood to be there physically -- imagining that the sign is written in Ylian when all that you see on the display in front of you is words in English breaks a suspension of your disbelief in the game world. The player is made to imagine something as if it were not, and it's a minor little dent in the RP experience.
On the other hand, text in the chat box is simply understood by everyone as a
translation of what is spoken in the game world, no different than subtitles for a foreign-produced movie (it's just that in Planeshift's case, we don't actually
hear the foreign voices at all).
Be understanding please, the art isn't something that can just be changed by anyone.
Of course not, just the art team.