I don’t know what you’re using, I’ve seen them be quite competitive in terms of pricing despite their lower density configuration.
No way, in terms of revenue, they’ll get a pretty decent boost. The weight and balance can be solved with the additional passenger bags being loaded into the front hold. Cathay has a very generous passenger baggage policy. The added fuel cost is negligible, as demonstrated with Air Canada and Air France both cramming around 450 seats on their 77Ws without having any noticeable change in mission capability.
I don’t think any airline is trying to keep a reputation of good service anymore since it doesn’t contribute to the bottom line. Cathay would’ve kept the 9-across configuration if people were willing the pay the premium to make it worthwhile.