One of the (many) problems is matching the size of the cabin with all of the supporting infrastructure. Everything from check-in staff, to catering, to on board service with the standard number of crew. Quite well handled today by the CSM/D who came round and took all of the GCH's choices first, probably in anticipation of first choices running out.
So far though, there always seems to have been plenty of luggage space with a big cabin - something to do with having only 4 pax per row for more rows I suppose. I guess club pax might also check bags, since they have the allowance, compared to a fair number of HBO fares down the back.
As for the ability or otherwise to move the curtain, and reconfigure at outstations, the aircraft came out with 8 rows of club and went back with 13.