- I believe O'Brien was just addressed as 'chief', so he could still be a SCPO, or have been promoted at some point to MCPO.Off the top of my head, did "Force and Motion" happen to mention if Chief O'Brien was still a Senior Chief Petty Officer or if he'd been promoted to Master Chief?
Interestingly, David R. George III seems very particular about discerning character's ranks in his novels. Particularly those of lieutenant commander and commander rank, which is very considerate

I recall that Counselor Philippa Matthias was mentioned in Ascendance and confirmed to be a lieutenant commander; and Wheeler Stinson and Jefferson Blackmer were also confirmed lieutenant commanders
(although Blackmer gets a promotion from security chief to first officer, but it's not made clear whether it was just a promotion of position, or if there was a promotion in rank, too - I guess we might find out in the next DS9 book, The Long Mirage?)