Honestly, I think the biggest problem is that Colm Meaney and Rosalind Chao have negative chemistry. They probably cast her in TNG thinking that O’Brien was a second-tier supporting character, and that she had good “nervous bride” energy for her first appearance in “Data’s Day,” and that would probably be about it for the character. It’s not the actor’s fault that a fictional pairing that wasn’t very well thought-out on the writers’ and casting director’s part didn’t turn out to be strong enough to survive as a primary plot driver.

That said… I would have loved to see Miles and Keiko go through an amicable divorce. They virtually did, between Keiko basically throwing Miles and Kira together during their pregnancy and Keiko’s long-term journeys to Bajor. It wouldn’t have been that much further to just have them realize that they’d grown apart and agree to separate, and it could be a way for Star Trek to explore a subject that a lot of people had real-life experience with. I don’t suppose that mid- to late-90s Star Trek producers would have gone for it, but there was some real narrative potential there.