Just did this, but wanting to use a companion pass I had to call in (matrix brings the details up on AC.com but I couldn't apply the companion pass without repricing the itin which bumped it down to a non-instant upgrade class, presumably K). Anyhow, I got a switched-on agent who booked into B at my request, applied the companion pass, and after I was able to upgrade 3 of 4 segments . The one waitlisted is a domestic connection which I expect/hope will clear, as J9P4R0 & the seat map shows 2/28 reserved, and its 6 months out. Saved ~$2000 compared with J alternatives I was looking at, which were for non-preferred dates.

The other aspect of ex-Europe flights is this: There are great deals still to be had originating in Europe for multi-city itins, which we have and will take advantage of. Last year we flew on a version of this deal, and provisionally there are LH flights that will take us to/from both Europe and Australia for ~7k in paid J for 2025/6. That may be of less interest if you are hell-bent on flying AC metal, but AC's cost is >$20,000 in comparison