The new Dec '22 structure allows for a 1tph Chester path.
Remember that the new stock to replace the 221s can't tilt, so the further it runs along the WCML, the more time it looses. Bar 1tpd to/from Blackpool, I don't believe any 80x's will get past Weaver.
The changes to the paths north of Preston are pretty limited. Based on 390 v 397 timings, the loss is only ~5 mins, but that could well be the difference between getting a path or not through the Glasgow suburban area, or Edinburgh.
Basically......don't combine the Wales and Scotland services.