I tried to read most of the thread, and the first page in detail so if this has already been mentioned sorry. It seems a lot of discussion is going on related to the effect the club face orientation relative to the swing plane at various points in the swing has on ball flight. Starting from impact and working our way back, we agree all the matters is your club face at impact. The question isn't whether the club face at checkpoint A or B has an effect on ball flight, its whether it has an effect on club face orientation at impact (which would then have an effect on ball flight). It seems the discussion is centered around the timing aspect of this effect. That is, rotating your club face away from is eventual perpindicular-to-swing-path position at impact could make your swing harder to execute and therefor less consistent. Obviously this is open to opinion (perhaps), and might and likely is different for everyone.
However it seems to me another reason that the club fact orientation might (should?) change during the swing has to do with how your wrists behave in keeping your shaft on the swing plane. I used to have an issue where I would keep my club face (or attempt to keep my club face) perpindicular to the plane the whole way, but it caused me to have all kinds of wrist breakdowns at the top-of-the-swing and transition area. I honestly just don't see how you can have the right wrist situation at the top of your swing and during your transition without having your thumbs pointing along the swing path (i.e. your right forearm--for a right-hander--should be kind of pointing in the same direction as your face, how can you do that if you keep your club face perpindicular to the swing plane?).
Basically my point is I think rotating the club fact may mean you have to work on timing which may make your swing more difficult, but its done for a reason (to help your wrists at the top-of-swing and transition) such that the benefits outweigh the added timing difficulties.