If the Wales & Borders franchise sees most of its 75mph DMUs (142/143/150/153) replaced by EMUs in the Cardiff/ Swansea area then it's going to be left with a small and geographically disparate number of "local" DMUs to run Blaenau Ffestiniog/ Bidston/ Crewe/ Heart of Wales/ Cheltenham/ West Wales services (would it be easier for the slow services in north Wales/ Cheshire area being moved to "Northern" for operational reasons, rather than running 150s all the way from Swansea when something goes wrong?).
The Blaenau Ffestiniog branch is always going to be a problem in terms of microfleets I think. It's one or two 75mph diagrams in the middle of a main line which sees mainly 90-125mph stock. How much of a depot is Holyhead? If it is substantial enough, you could maybe introduce a Llandudno - Holyhead stopper but it still probably would be a fairly small fleet based at Holyhead (still might not even make it into double figures). There's a similar problem futher south with the Cardiff - Cheltenham service, unless it is transfered to the GW with their 165s/166s or worked by the regional express units off marches lines workings (which would be a bit of a waste if you ask me).
Assuming the 153s are converted back into 155s (that being the only hope for them as TSI-PRM compliant units I suspect), my view is that Wales & Borders' Swansea-based 75mph fleet should consist solely of a single class, which should either be 155s or 156s. Those would work west of Swansea and the HOWL line services, possibly extended through to Crewe as the stopper. The Wrexham-Bidston and Crewe-Chester services probably belong with some other TOC. 150s in my opinion (and Pacers) are only suitable for journeys up to one hour duration, and there'll be very little of that left in Wales for 75mph DMUs once the valleys have been wired.
If new 390s are built for London - Blackpool/ Bolton and London/Birmingham - Glasgow/Edinburgh then does that mean the WCML franchise will only have a token number of Voyagers (enough to run services to Chester/ Holyhead)?
Virgin proposed no Voyagers and diesel-electric locos would be used to serve non-electrified destinations.
What happened to that? I thought that now VT has a direct award they would be starting the process to order the planned 21 new EMUs to replace the 221s. While I can't recall how long the direct award is, presumably whoever takes over the franchise long-term will be needing the new stock given both franchise bidders planned to introduce some.
each of GA's diesel fleets could be described as a microfleet given the small number of each that they have.
I was going to say something like that. Both their sprinter classes are in single figures (says wikipedia) and they don't have that many 170s (12) either. Mind you, the 170s seem to be a fleet of 'microfleets', with only the /4 and /5 subclasses exceeding 20 units.