hi! thanks for joining the discussion. excellent to know that there are others who are also trying to figure this out. very cool..
sorry i should have been more clear in my explanation. the variant 15 i'm referring to is not going by the list you have there, but the language file number that you see at the flash screen on the 2nd row with the pull-down menu. for example, by default, my firmware is:
0529664 Euro-E1 Silver
if you check the language file name you would see a number ".... V5...", hence my reasoning that V.5 is english/spanish, exactly what my phone had came with. and if you check - 0524755 Apac-R Silver SG - you'd see that it's variant 19, same as 0530024 Apac-R Silver. both of these are simplified chinese. which goes to show that what really matters to us end users is the language file number.
during my process of reflashing the phone to traditional chinese, it was clear i should look for something with APAC-*... but if you check the language file number, you would notice that for all the APAC firmwares they associate ONLY with variants 17, 18, 19, 20, and 21. personally so far i've had experience with 19 (simplified chinese), 18 (traditional chinese HK) and 20 (malaysian, filipino, etc...). i've yet to try 17 and 21. my guess? well, there's still at least two major languages left in asia: japanese and korean. so they could probably fill that.
but i'd seriously love to hear if someone's actually tried that.... who knows, maybe i'd get lucky on traditional chinese (phonetics) on either one of those.
anyway... so to me the sequence of the list doesn't seem to matter too much because there's no specific reasoning behind the sequence, so this is what i've been following so far. heh, i could be thinking this all wrong, but this makes a lot of sense for me.
hope this helps! feel free to share some more