Nothing about full length buffets broadgage?
I agree, capacity is the number one issue before anything else.
Being a little picky though, and actually a disadvantage to longer train lengths is the situation at Reading. With full length crossrail trains, services are more restricted for the use of common platforms 13 & 14 whilst anything longer than a 5 car voyager rules out the other common Platform 3, which is the perfect platform for
XC▸ services at the moment and therefore would make that platform pretty much redundant. More careful planning will be required.