The OSISVariants filter looks to be copied from the ThMLVariants filter. I don't believe it works on anything, and it doesn't function on text that would be valid OSIS.
I've put a module into testing (Tisch) which makes use of what it calls Qere readings. There are about 5 in the entire text, but presumably they will appear in greater number in later versions.
They are encoded analogously to lemmas and are encoded in the lemma attribute on the w element: variant.<type>:<form>
For example: <w morph="robinson:N-PRI" lemma="strong:G4466 lemma.Strong:Ῥαγαῦ lemma.ANLEX:Ῥαγαύ variant.Qere:Ῥαγαῦ">Ραγαῦ</w>