There are better ways IMO to address the stock shortage problems, and personally I'd say that a big one of them is the production of a new series of LHCS that can be diesel hauled, electric hauled or both.
Reigonal branch services can be hauled by a freight locomotive, god knows we have plenty going spare, mainline services over 75mph (diesel) can be hauled by a new series of Eurolights running at 110mph, easilly do-able and will be needed for years to come on the GW Cornish services etc. Anywhere that frequently uses formations of 5, 6car or longer DMUs will move over to LHCS, the HST replacements would be these as well, possibly seeing if one can push the speed on Diesel up to 125 with two locomotives. (Or simply change from Leccy to Diesel Loco)