The current timetable works with one sat in Queen Street for 50 minutes in an hour, and another sat on the branch at Grangemouth for 30 minutes in an hour. It's not the most intensive use of resources, hence why it only required one extra diagram to run the whole thing through to Edinburgh.
To add, we could do the 'via Grahamston' services with a nine minutes turnaround in Waverley, and a mostly 12 minute turnaround at Queen Street. The departures from Glasgow were never perfectly even, they were always timed for a minute or two pathing time at the top of Cowlairs tunnel, inevitably waiting for something to come into Queen Street before crossing over the down line.
Unfortunately, I don't remember what the service timetable became, but we spent about three months in the EGIP planning rooms fitting it all together; the timetable, the infrastructure, and the planning. The final product was one of those rare moments where it all did come together to create a very comprehensive service across the board. Its a shame COVID came along and suddenly it all fell apart when the next lot of investments got kicked down the road a few years