I really miss the benefits of OW Emerald (I had BA Gold for a long time) when I fly on *A partners. Every time I fly NH (once or twice a year) I stare longingly at the First Class check in and lounges that I don’t have access to (as an SE AC*G). I begrudgingly accept it makes sense that *A doesn’t have a Platinum tier, as so few *A carriers have First any more, but it’s hard to not miss it once you’ve had OW Emerald. Also, so many OpUps across the OW alliance as an Emerald!

EDIT — OpUps into First! Used to LOVE that beeping alert that the BP scanner would make when boarding which signalled a seat change (again, OpUp into First)