Liverpool gets an hourly Pendolino service and Edge Hill justifies being used as a stabling point (long ECS move from Edge Hill to Longsight...).
Glasgow doesn't even get an hourly Pendolino service but Polmadie justifies being used as a stabling point (even longer ECS move!).
Any reason why Chester (which would have an hourly Pendolino service) wouldn't justify the same?
Chester doesn't have any Virgin crews based there and considering crews are based at Liverpool, Manchester and Crewe it's unlikely that it will become a base for them.
It also has an earlier finish for London services, so the chances of finding a path for an ECS move would be more difficult.
There may also be platform issues at Chester with having more terminating services from London and replacement services to Holyhead. There's only 3 platforms that could take a Pendolino and one of them has a Merseyrail service departing from it every 15 minutes. If a Pendolino takes up one of the three then it only leaves one through platform for other services.
By the same logic BR wouldn't have electrified much of the WCML north of Crewe, due to lack of electrified diversionary routes. If you don't want to wire a route because the diversionary routes aren't wired yet then no new electrification would be justified.
When BR did electrification they knew that during weekend engineering works they could swap an electric loco usually used on WCML passenger services with a diesel loco usually used on weekday freight services to send the train an alternative route e.g. via Bolton.
You seem to be suggesting a 100% electric fleet for the next WC franchise with a few diesel locos. A 100% electric fleet works for a local operator like c2c but won't work for regional and intercity franchises unless we have much more electrification.