Virgin's best way forward, certainly in Scotland, is a part or full week based aircraft
I'm not sure what you mean by this, but if you are suggesting a weekly frequency (one rotation a week) they don't work as the higher revenue passengers require the flexibility of a daily service, so the lower frequency services primatily attract low revenue passengers.
The common misconception is that if you are 50% filling 7 flights a week you can 100% fill 3 flights a week as that is (roughly) the same number of passengers. It doesn't work that way, you will lose passenger volume as they spill onto other carriers offering better flexibility.