The upgrade philosophy of USA and non USA airlines is very different (all alliances)
AA & AS have cross airline upgrade now
AA and BA/IB have cross airline upgrade now. (but not BA<--->IB IIRC) ----> AA Partner Airline Upgrade Award - BA, IB, including codeshares (master thd)
Both have onerous t&c's

As your article, for those airlines using avios (QR BA IB AY) as the ff currency may be a little easier.
The method and cost of an upgrade on the airline of your ffp varies a lot. Will be hard to get a common *fair* value to all
Given the cost of QF awards and upgrades, compared to other fftp's, struggle to see any benefits for QF freq flyers.
Will benefit "frequent spenders" and not "frequent flyers"'

Edit
AA thread-- AA FF members soon to be able to book alliance-wide upgrades