Renaming "Common" language?
 

Common as a language is a holdover from early D&D. The "Common" language of the Inner Sea is Taldane. How can I have it displayed as "Taldane" or "Common (Taldane)" or similar?

I know I can set it so there is no common language, allowing regional campaigns to show Variasian or similar, but in those campaigns there will be characters which know Taldane in addition.

Two things:
1. "Common" is the general language specified in the PF Core Rules, its not just a "holdover from early D&D".
2. While you only see "Common" - in HL PF, it actually has the description "While Taldor has lost much of its former glory, Taldane (Common) remains the primary trade language of the Inner Sea region, spoken and understood almost everywhere."
Admittedly, you won't see this unless you actually choose "Replace Common" and then look at Common on the menu.

That said, you could try replacing the Common language with your own version, or try to over-write it with a mechanic and something like
perform state.thing[lCommon].amendthing[name, "Taldane"] <Guessing "lCommon" in the script>

Only stuck-up Taldans would bother calling it Taldane.