OK now, I have an offical anouncment to make here in the right place, the s1mp3 forum:
The Serbian cyrillic translation of ALL the textual options for the "Blueberry" brand s1mp3 mp4 player is COMPLETED.
It gave me a lot of wrestle, trouble and struggle, but finally I totally NAILED it down.
The order and place of the characters (the difference between standard (PC) and s1mp3 fonts) gave me the most of trouble, but I solved that with the ultimate solution, heh, heh, it didn't stand a chance.
Now I have the character conversion table, the .txt list of all the phrases in the translation AND the actual 'dump.bin' file - all nice and tidy (the exact number of letters was removed from other (unneeded) language translations (sacrificed were: Spanish, Portugeese and Netherland... oh, and Russian) in order to make space for the Serbian translation symbols). Of course there is still that lousy half-a**ed latin-script "Serbian/Croatian" excuse for a language translation that cam with the player available (phhh... most things aren't translated at all).
My translation is complete and utter rewrite. And it's cyrillic!
Which is nice (also, from this one I can easily create latin-script version - no problem) It took A LOT of work, but it's finally there.
Completely different issue: I still don't like cirillic font on mp4 - because the "hanging letters" (such as 'p' or 'y') are raised, but it's not that bad (except some lower case letters look like upper ones... darn it), so, if someone can locate the system font used on it - any help is appreciated!
If someone wants a translation for some other cyrillic language (such as Russian, Ukrainian, Belarus, Polish, Macadonian, Bulgarian... Kazak... Whatever...) - I'm here glad to help. Just give me .txt list of translations and your firmware file, and I'll "put 2 and 2 together" what to do with it...