The Corby service is still going to be a major spanner in the works of any fleet homogenisation, as it will be electrified long before any replacement stock comes on-line.
It's still an absolute mystery as to what EMT / their successor are going to run on those services, since the DfT are insistent that whatever runs needs to be "intercity standard" to match the trip quality of the 222s. And of course, as a fully electrified route, it will be pointless operating a bi-mode train there, unless by some miracle the single daily Melton Mowbray via Harringworth Viaduct service isn't cut in the next franchise (spoiler alert - it will be). There are some "intercity" electric fleets coming off-lease around the time that electrification will be completed, granted, but the logic of picking up at most 5 or 6 trainsets from, say, VTEC, is flawed given there will need to be significant work done to prepare staff for their use, and have suitable facilities provided to maintain them, most likely for a relatively short stretch of time.
Whatever happens, they're going to have to either draft in a small, non-standard fleet to work those services at fairly short notice or keep the 222s on the diagram. The latter, of course, completely defeats the point of electrifying the line in the first place.
In the medium term, they'll probably just set bi-modes to work on the route for the sake of wider network flexibility, but beyond that being a pointless waste of their capabilities, the fact remains that, at the current rate, there's going to be a gap, potentially running to a few years, between them electrifying to Corby and acquiring a fleet of trains capable of utilising the new infrastructure.
Of course, none of this would be a problem if the DfT would just swallow their pride and either drop the need for the "intercity standard" stock, or transfer the route to TL.
PS: As for comparison of unit power, we should really be comparing 800s to 222s, which are better performers than the HSTs in most metrics and likely to become the staple of the EM franchise's operations within the next 3-5 years. Given that the jury is still out on how they compare to HSTs on diesel power based on performance recordings on GWR, it's worth noting that they'll be expected to meet a more intensive timetable from 2019, do this on a network which will, at its zenith, still have more than 50% of its route mileage away from the wires and will be expected to do so alongside units in the 222s which are operationally superior to the HSTs they've exclusively been replacing on the GWML.
In response to D365's post, a 222 by comparison pulls 3750hp with a 5-car unit. Not that this matters as much as their acceleration rate, which at 0.75m/s/s is above what a HST can manage - and even further above what an 800 can seemingly manage on diesel power!
