It would be pointless, as they are not planned to run down the B&H, and you wouldn't really need a 9 coach train on the Cotswold's services, the Cheltneham's and for services beyond Swansea.
It simplifies things - instead of having four types of trains (long and short versions of electric and bi-mode) we will have five coach bi-mode and nine coach electric - which should make things a lot easier and encourage portion working at the extremes (you need a nine/ten coach train from London to Reading/ Swindon/ Oxford etc, but generally not all the way to Hereford/ Carmarthen etc).
Have either of you ever travelled on peak Cotswold Line services?
There are several peak trains which are full or near-full HSTs arriving from the west into Oxford in the morning or heading back west in the late afternoon and early evening, never mind the loads between Oxford and London.
Due to short platform lengths between Oxford and Worcester, 2x5-car formations with no corridor connections simply won't work and trying to increase peak frequencies to spread out passengers over more trains would require heroic punctuality, due to the constraints posed by the remaining single-line sections, so how on earth these busy services will be operated is a mystery, unless the bidders go back to DfT and tell them that longer bi-mode formations are needed.
The tender documents do say they will still listen to suggestions about the formations, so it is to be hoped sense prevails and some long sets do indeed appear in the GW fleet.
For all those going on about 'unnecessary' bi-modes, not all diagrams are 'captive' to specific routes - as things stand, HSTs that spend much of the day on the main line also fit in Cotswold/Cheltenham turns to add capacity in the peaks, so making an allowance for such things to continue with new trains is surely sensible.
