I'll for sure not translate XYplorer (since I do not think that there would be any more interest for a non-English XYplorer in the speaking areas of the languages known to me) but nevertheless I am a fan of your format.
It is very similar to something I have conceptualised some years ago while developing something with Delphi (but run out of time and energy before it ever got out there in the world). Would the coding be UTF-8? In my application (the one which was dead before birth, so to speak), I was easily able to switch GUI language on the fly, without the need of closing application.
Personally, I was always wondering why that mess with resource strings and the like. So, if I were you, I would definitely go the way you are suggesting.
(But, I admit, I have BeyondCompare and would probably be using it for tracking your possible daily introduction of new strings to be translated. So, maybe it would not be a bad idea if you would conceive a system of pointing out the newly introduced strings for existing translations, in order to facilitate keeping translation in sync with your development.)
Win 7 Pro 64bit