I absolutely agree; I've argued before for a cascade plan like this:
- Electrify GWR to Bristol (both ways), Swansea, and Oxford
- order new 125 mph EMUs for the South Wales, Bristol and Oxford ICs, at least 260m long
- Cascade the excess 5-car GWR 80x to XC, keep maintenance at current depots (rewrite XC diagrams to accomodate)
- Increase the LNER order from CAF, both in length to at least 260m (longer might be possible on LNER, but I'd have to check), and in number sufficient to replace all bimode 5-car 80x, assuming CAF is willing to do that for a reasonable price.
- Cascade all LNER bimode 5-car 80x to XC, keep maintenance at current depots except London, rewrite XC diagrams to accommodate
This way, LNER and GWR have new, higher capacity to use on their busiest services - expanding capacity without needing more paths. XC get higher capacity, more efficient, and nicer units for their services, and start to take on some of that suppressed demand