I would be all for 165s/166s being used on Birmingham regional services. Birmingham - Hereford/Shrewsbury is only similar to London - Oxford/Reading which they are already used to doing and they are not as uncomfortable as is being made out (they are hardly 142s).
I would like to see this happen:
21x Class 166 GW - LM upon electrification
05x Class 165 GW - LM upon electrification
Then:
09x Class 170/5 LM - EA
09x Class 156 EA - Northern
09x Class 142 Northern - Withdrawn
08x Class 170/5 LM - GW
06x Class 170/6 LM - GW
08x Class 143 GW - Withdrawn or Northern?
06x Class 150 GW - Northern
06x Class 142 Northern - Withdrawn
I would propose at looking at the centre coaches of the 170/6s being added into 170518 - 170523 of Cross Country (removed from 170630 - 170635) as then you are helping BHM - SSDs out.
I have also accounted for 26x Turbos to go to LM to account for growth and to prevent overcrowding and I think I may have overaccounted for them (annoyingly their are 21x 166s whilst LM have 23x 170s)
Of course, the Turbos would have to be able to be cleared for all these services:
Birmingham New Street - Hereford
Birmingham New Street - Rugeley Trent Valley
Birmingham New Street - Shrewsbury
Opinions on this of course welcome.
The 166s would be well suited to the Chase Line and Shrewsbury services, and wouldn't fare too badly on the Worcester and Hereford services either IMO: The distances and journey times involved for the longest Hereford services are little different to the work the Turbos currently perform on Oxford and Cotswolds services. I think twenty one 166s would be perfectly capable of replacing LMs' twenty three 170s with only marginally tighter fleet rostering, as I suspect that London Midland have a comfortable amount of slack in their 170 fleet considering how many of their units can be seen sitting at Tyseley outside of the peaks.
Using the three car 166s on the Chase Line would do away with the need for pairing units up with 153s to make three car trains, although the downside of this is that four car trains would no longer be possible on the Worcester and Hereford services, and I'm not sure all of the stations along that route could cope with six carriage formations. More than three carriages is definitely needed to cope with passenger numbers on the busiest trains.
170630-635 could then go to Crosscountry, giving XC the entirety of the 170/6 three car fleet, which would replace 170518-523 and leave the whole 170/5 fleet of 23 trains to go to a different operator: Great Western perhaps. This would leave 170111-117 as two car units with Crosscountry, which works out well as XC also have a requirement for some services formed of more than three coaches to cope with demand.
The eight 143s should go to Arriva Trains Wales IMO, giving them the whole twenty five strong class 143 fleet to boost capacity on the Valley Lines and release some 150s for other services pending potential electrification of the Valley Lines. This would make withdrawal of the entire 143 fleet a very simple procedure upon electrification.