as a modder, I think it would be nice if it was possible to define a "default" language that is used if no proper string in the chosen language is defined. is that in any way possible?
because I think it would be nice if people not playing in en-US could still enjoy some name for the new strings, even if it's not in their own language, it is definitely better than the "STR_WHATEVER_SOMETHING_OR_OTHER" clogging up the research/manufacture/inventory/ufopaedia screens...
and I will definitely not bloat my mod rulesets with a several-page-long string name list for a load of languages I don't even understand...