It is quite interesting that by 2014 there are relatively few people who remember the rail replacement services put on at the time of the Beeching cuts, and judge them by the completely different circumstances and standards of today!
Many of the trains, on some lines virtually all, carried very small numbers of passengers; certainly not enough to make a replacement bus operation viable.
Many of the lines which were closed already had bus services operating in the area, not necessarily parallel, but competing between at least some of the station pairs. In most cases these services were operated by companies in common ultimate ownership (i.e the Government) but were managed totally independently from the railways and expected to make their financial way in the world. These bus services were often the main reason for the lack of local custom on the branch lines, particularly if the junction station was in an obscure place, such as Gwinear Road, Brent or Sidmouth Junction, as passengers would rather ride (an often) more frequent and direct through bus than make a change to an possibly unpunctual long distance train.
In 1964-6 (the main years of the Beeching cuts), the bus companies were losing (particularly off peak) passengers to private cars and changing social circumstances at an alarming rate, and often viewed railway replacement services as a threat, partly through possible abstraction of passengers from their existing services, and partly due to the staff shortage issues that plagued the industry at the time. Changing the structure of the services to minimise the costs of the rail replacement services was not even considered - this was a risk and would take an age to get through the Traffic Commissioner - after all the Railway would pay a subsidy for the first two years, during which time the bus company could attempt to cover any worthwhile flows by changing their existing services or even retaining the service commercially in a few cases. Connecting long distance rail passengers would be few and subject to railway timetable changes, punctuality problems, luggage etc so were not practical on an ordinary service bus anyway.
When the TUCC examined the railway closure, the surrounding bus services were considered and the Railways wanted to minimise their subsidy risk (which Government had limited to two years anyway) and the bus companies wanted to minimise disturbance to their existing services (and their delicate financial situation). So replacement services were only run where there was no existing adequate service (adequate being de facto 'was there a service between A and B', rather than specifically for connecting to the rest of the rail network) Hence many replacement services ended up running between closed stations and junctions that no one wanted to go to, replacing trains that no one was riding on anyway. Of course, on some lines [Bodmin Rd-Bodmin-Wadebridge-Padstow springs to mind] the rail replacement service continued long after the subsidy disappeared, but most did not.
Some lines merely got token extensions of existing bus journeys from Bus Station to Rail Station, sometimes connecting with trains at inception, but the rail timetable was unstable, the railways often did not inform bus companies of timetable changes until too late, and anyway the vast majority of passengers were travelling locally and the buses would run at times suitable for them, rather than train connections.
On some lines (Cambridge- Bedford for instance) the replacement service served at (or near) each of the stations [many of which must have produced few passengers for the train] along country roads and took a lot longer for end to end traffic than the existing bus service via a completely different route.
Of course it would be possible to operate the type of services referred to by the OP, but this implies an increase in transport subsidy, unless it is used to replace existing branch lines at a cheaper cost. Now that's controversial.......
