The real big issue you stumble into if you have full nationalisation is that the treasury hold the purse strings for the railway and that undoubtedly the one of the first things that would be cut if savings needed to be made would be to the railway budget on day to day running. I'm not talking about capital investment. At least with a franchise or concession or whatever you want to call it the treasury does not control day to day spending. Yes reform the franchise system so private companies have to up their game. If the railway is running at a huge loss and has to be supported by subsidies then maybe a serious look needs to given to the services that are making a massive loss. It may be the case that some lines are told "use it or lose it" like what has happened to a lot of bus routes that were hardly used.
In your opinion , how would you incentivise franchisees or concession holders to up their game?