The bus timed fare is a good idea, would be possible, and I believe a green candidate pledged this in one of the recent mayoral elections, but it requires leadership containing intelligence and foresight- departments which I'm sad to say our current mayor is sadly lacking. The 'dangleway' over the Thames is an obvious example.

However, I was recently in Tokyo and the transport system there while clean, punctual and frequent is a bit of a mess when it comes to paying for tickets, in some cases you cant exit gates unless you buy a separate ticket, and some lines require different tickets!