Thank you, JSanders.
The good news is that it was yesterday that it finally dawned at me, right after my post above, that, in fact, I speak Russian, though not very well, so I asked google in Russian
and quess what?
The moment we speak I have a fully functional cyrillic support and input.
The Russian keyboard layout is a bit different from Bulgarian, and they have two more letters, but that really doesn't matter.
Well, the other side of the story is that I had to downgrade from .113 to .114 because that was the latest possible All language OS I could get to. But with my cyrillic keyboard I can now happily wait for some official OS release, with maybe directly Bulgarian support.
The funny part was that the tech support from MTel/Vodafone here in Bulgaria told me that there is absolutely no way of having cyrillic input.