Statement A is odd. We would not combine "(not) suppose" with "may", as both words modify the main verb in different ways.
People say this:
"I don't suppose he's (he has) even read the book, has he?"
This could be in a situation when you expect "him" to have done very little, not even read the book.
Statement B doesn't feel right with a tag question like "mustn't you?" or "haven't you". I never hear these. As "must have + past participle" is about logic and thinking, I recommend this tag question:
"....., don't you think?" This sounds natural.