I'm thinking it's time to admit defeat on the 170s for local services. Clearly they aren't cut out for it, certainly not on the Robin Hood line.
I remember moving to Manchester at the peak of the Northern crisis. Things have actually improved significantly with a slightly reduced post-covid timetable, Manchester-Blackpool electrification, reaching a deal with strikes and the introduction of 195s/331s and removal of Pacers (lower capacity, but they were unreliable and frequently block tracks/platforms).
I'd say that while EMR is in better shape than Northern were at that point, at least with Northern there was some kind of long term plan moving forwards. Unfortunately this is EMR's long term plan, which leaves me feeling sceptical as to whether improvement will come.
The cheapest solution would be to swap all 158s back to regional routes and put 170s on Liverpool/Norwich and perhaps Derby-Crewe (basically routes with higher average speeds/station spacing).
The second best/cheapest solution would be 195s.
The best solution would be electrification of the MML, Hope Valley and then using battery range extended EMUs for pretty much all of the regional service.
The 170s aren't that bad (though they're tired). A big thing is the tiny tweaks to the schedule that have a big impact. This shows across all the routes. All of those little improvements and bits of padding put in the right places over the years have gone in favour of over ambitious flat minimum timings all over the place. Going back to a 15x timing load even with a 170 would help.
You can see it across the routes.
3 minute turnaround times with 4 car trains at Grantham during the peak Skegness holiday season.
The loss of the Robin Hood line late night padding that is essential to get rid of the drunks licking the windows at their mates inside without losing time.
The change to the RHL schedules entirely that muck up journey opportunities and slaughter the single lines.
2 and 3 minute turnarounds on the Crewe line at Derby with minimal time at Crewe and Newark.
Trains booked to use platform 1 at Sleaford to run from Peterborough to Lincoln during the day making minimum time connections or sub minimum time with trains to/from Skegness, giving either ludicrous journey times or making it impossible for anyone who can't use the footbridge to change trains.
The full unreduced timetable makes Nottingham and Lincoln unmanageable maelstroms of shunt movements that absorb lots of resources in their own right, particularly platform staff and depot drivers at Nottingham to kick out and shunt units.
It was all very nice on paper but many long standing connections have been wrecked and there are innumerable problems with the schedules that will remain difficult regardless of whether you're using any kind of DMU.
Replacing the 170s will make no difference to any of that.
