I think it makes more sense to move UC to the Upper Deck, as I can not see them moving UC back and all the Y class pax going through to Y and the noise factor. I really wouldn't want to be flying UC if they move it back, with the noise and all the Y pax going through. Lets hope the service doesn't go down hill [:?][:?]
Another option might be:
Put 10 extra J seats where the W seats are now on the main deck = 54J
Remove the front Y cabin upto row 38 as before -82Y = 228Y
Put 6 rows of W seats in that cabin as 2-3-2 = 42W seats, with the 20W seats already on the Upper deck = 62W
Just another guess though!!!
Regards