I wouldn't book these for the last point you mentioned. However, I have been approached to see if I would like a row to myself being the only gold in the cabin. You could also proactively ask and see what happens. I've had about a 50% hit rate by doing the latter.

Although it's a long flight, you've got one of the best aircraft for it in Y in my opinion. For the record, I flew back the other week in Y on the A380 from BOS and it was remarkably more comfortable/spacious than the 777 on the way out. I overheard some discussion from the cabin crew as we exited the plane about the lower deck, which I was on, having more overhead space and how the dimensions are generally bigger downstairs. You may therefore wish to switch to the lower deck? I found the exit row perfectly adequate.

Also- sounds like the flight is pretty full overall, so with some potential no shows, changes etc- you might get an op/up anyway. Yes, you'll arrive less refreshed but on a new BA aircraft you'll also arrive thinking that really wasn't so bad.