I do not have enough expertise to evaluate the need for specific codes, but on a general level
- All language codes could be included, so I definitely support adding sjk as well
- Source materials may exist in Cyrillic form only, so I support adding them as well
- Source materials may only exist in oral form without orthography, thus being able to record whatever is available would be important. I do not know the existing practices for recording phonetic transcripts, in my opinion they should be supported.
- UPA is more commonly used for Uralic languages than IPA, and deciding which one to support would be beyond my knowledge