I’ve watched this thread with interest, to see which franchises were chosen, and for what reasons. Of course, some haven’t given reasons.
For me, you have to break it down into what, exactly, does a TOC manage? In simple terms it is people*, contracts, stakeholders, and of course passengers. It follows that the more people, more contracts, more stakeholders, and more passengers you have, the harder it becomes. Taken further, the more different types of people, contracts, stakeholders and passengers, you have, and their geographical spread, adds to the complexity and therefor difficulty.
Using this model, I would say that the easiest operations to manage, excluding the open access guys, are:
c2c
Merseyrail
Chiltern
Southeastern
All have relatively compact operations, with relatively few contracts, few stakeholders, and (southeastern aside) few passengers. Notably all have remained almost identical in terms of routes and geography operated since privatisation, indeed the history of their organisation can be traced back at least a decade prior to that.
Why is Southeatsern on the list? It’s almost completely self contained, with little interference from other operators (a bit of freight, a brush with GTR, LO and Eurostar), close alignment to major stakeholders (NR Kent, Kent CC), and the vast majority of the operation is London focussed. Although there’s a lot of people in the franchise they are within a small geography which means that many of the activities are interchangeable. For example, most drivers sign the routes into at least 3 of the London termini. (Oh and there’s not many guards to worry about).
The hardest:
Northern
GTR
Cross Country
GWR
All with huge geography, lots of people (spread thinly), multiple contracts and hundreds of stakeholders. All have had their networks changed over the last 2 decades.
*Of course, you don’t manage people. You lead them. However a key part of managing a TOC is industrial relations with the unions, and this varies widely across the country. But that’s for another thread.