I've always thought that they should take all the bus routes out of
Oxford Street and instead run a free service with the preserved
Routemasters (or RTs, for that matter) between Marble Arch and
Tottenham Court Road.

So that everyone who shops there has to change bus at least once to get
home?

Or they can do what anyone else with more than half an ounce of common
sense does, and avoid shopping in Oxford Street (especially at this
time of year!)