It's just a suggestion of a route where a three coach DMU that's good at climbing hills would be okay - if anyone has a better idea for where fifty one of them would work better long term then fair enough - they have advantages and disadvantages on most lines though (they are shorter than the four coach 158s that used to provide most Leeds- Manchester "fasts")
The difference between Calder Vale and Buxton is at peak times Buxton line is pretty much all 4 car in the peak flow direction and obviously the trains that go to Buxton in the evening peak, have to come back at some point. Calder Vale sees a mix of 2, 3, 4 and 5 car, given the 5 car ones are booked as 144(3)+144 (2) or 144(3)+142 we could simplify that to 2, 3 or 4 car for practical purposes.
Would the Calder Vale fasts be able to run as 6 car without a whole scale platform lengthening scheme?
Another idea may be given the size of the fleet is small to rework the 185s to run on 2 engines and then use the removed engines for spare parts instead of ordering what could be costly spare parts in the future to keep 185s going.