I don't understand the use of Cyrillic voiceless consonants to represent Korean unaspirated lax consonants in stem-final position. For instance, буйөбатассъымйө for 부여받았으며. According to your guidelines, the т here represents either [t] or [tʰ](*), but neither is correct; the sound is actually [d].
What makes this choice all the more mystifying is that many languages written in the Cyrillic alphabet have a rule which devoices voiced consonants in final position. For instance Russian не забуду [nʲɪz̪ʌ'bud̪u] "I won't forget" vs. не забудь! [nʲɪz̪ʌ'butʲ]. If you simply extend this rule to Sirilgeul, then you'll have the correct alternation. E.g. баб [pap̚] "cooked rice", бабыл [pabɯl] "cooked rice [acc.]".
I also don't understand the logic behind the use of the hard sign to separate syllables. I can understand the need for this in a strict transliteration of the Han'geul, but it seems unnecessary for an ordinary writing system. "ссъ", "ъсс", and "със" will all be pronounced exactly the same, so what's the need to differentiate them?
(*) Ambiguous because you never give any guidelines for syllable division. You seem to be equating "syllable" with "syllable block in Han'geul", but for all I know you have a more cross-linguistic definition in mind.