True but given reducing rail demand will logically will put more people into their cars even if electric how does this fit in with the decarbonisation / emission reduction requirement by 2050.
Given that current electric cars (best emissions from road traffic) only broadly matches (on a per person per km) the current average of the rail network (including a lot of diesel use, which there's many battery support options which are cited as reducing diesel use by 20% and a lot of bimodal trains due to be delivered as well as ongoing electrification) it is likely that we'd still need to reduce car use (or at least not increase our car use by the circa 50% cited as being the likely increase by 2050) to reach net zero targets.
In the short term we need to grow rail use, or at least not do anything which limits the potential for growth. As such there is a need to increase capacity on XC.
Covid is likely to have a limited impact after about 5 years, at least in longer distance services like XC, however even if passenger numbers reach 2015 numbers in that timeframe there's still likely to be a need for extra capacity.
Using the existing 22x fleets, without mixing and matching, although getting rid of some end coaches, you could create a 13 x 9 coach 222's (plus an 8 coach unit) and a near total 5 coach fleet of 220's and 221's.
The 222's would give you enough to replace the HST's and the few services which currently run in pairs, maybe plus one or two extra services run as a full length train.
Having done that you'd have about 17 spare units to be able to run in pairs with other units, that may not sound like a lot, but it would probably allow about 1/2 the services to be 9 trains or 5+5 coach trains, with the potential for slightly more than half the services over the core to be run in pairs (assuming that the +5 part of the train turn around and coupled to another units at the edge of the core).
Although there would still be reasonable capacity uplifts just from upgrading from 4 to 5 coach units on those services which didn't see longer units in use.
In of you wanted more pairs of units you could retain the 220's as 4 coaches, however that does require more dept space, more track access charges and more maintenance costs for fairly limited increases in seating capacity. As such it'll be a case of balancing the benefits with the costs.
However given the uncertainty which HS2 brings to the XC services (for instance South Coast to Manchester woulld be noticeably faster, even though it would currently require two changes, using HS2 than the current XC services), then maybe it's worth seeing how HS2 starts to bed in, as well as what other electrification is complete, and then considering to start to replace the 22x's circa 2035 with bimodals units.
