As for the overhead crew rests, see this Boeing demonstrator plane:
http://www.airliners.net/photo/Boein...-LR/0864326/L/
http://www.airliners.net/photo/Boein...-LR/0887391/L/
See how much A300 sidewalls slope inwards above.
The upright B777 sidewalls means that they need very much space before they meet at the roof. A 777 is hauling around a lot of useless attic space. An A300 has much less wasted space in the attic - therefore not enough headroom for crew rest.
The only planes suited for overhead crew rests are 747 and 777.