I cannot recommend the hard-shell Premium Eco seats on the appareils serving KIX. Take a look at some of the other threads, and how unconfortable they are. No, I am not exaggerating; people would rather downgrade to Y than fly the hard-shell W.

For your question, don't think there is a way to see the flying blue miles required if you didn't have it attached in the first place. But often, there isn't a great correlation between the cash and miles required, as the offers vary from person to person based on their previous travel and upgrade history.