Good, no hestitation. In my view there needs to be more competition on the network. On any route where there is more than one train per hour the paths should be split between 2 operators so we get a choice. Yes, that probably means less fare flexibility but in return I expect better "service".
For many travellers fare flexibility is the thing that matters. As a season-ticket-holding commuter I just want to arrive at my local station in the morning and get on board the next train. I don't want have to wait for the one after because I have a season ticket for a different operator. I don't care if the train is painted blue/yellow or green/orange. I don't care if it has blue 2+3 or orange 3+3 seats [I'll probably be standing anyway]. I just want the train to get me to my place of work quickly without fuss.
OK so maybe you didn't mean commuter routes. But commuters use long-distance services as well, as these are an integral part of the rail service. What I wrote above applies equally if commuting to London from Swindon as from Kingston or Watford.
Likewise, if I wanted to do a one-off journey from Swindon to London today, I just want to go to the ticket office, buy a ticket and get on the next train. And if it's a return ticket, I want to travel back to Swindon on any train, not be bothered about which operator I have to use.
But why are there 4 or 5 trains per hour between Swindon and London? Because west of Swindon they split off in different directions. Having Paddington-Bristol via Bath and PaddingtonCardiff served by different operators might make for competition on the LondonSwindon route, but it would not be good for an integrated rail network in the West of the UK.
Or consider LondonManchester. There are 3 fast trains per hour on this route, so you could ask why can't they be run by 3 operators? Well, their stopping patterns are different, so they complement each other; as a LondonManchester passenger I don't want to care about this, I just want to be able to get on the next train from Euston that will get me to Manchester.
As for the effect on through ticketing... you can see what happens by considering how difficult it is to through-ticket flexibly on any journey that involves the BrusselsCologne route (where there are two operators with completely separate ticketing).
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IMO the franchised operators should just do the local/regional work, and provide at least a basic service over the whole network, and have the intercity network based on the open access principle. I believe that this could create a much further reaching intercity network with some REAL competition.
But most inter-city trains carry some local/regional/commuter passengers (look at Swindon/ReadingLondon). The inter-city trains complement the regional stoppers. What you suggest would take away the integration between these types of service.