I'd question the identification of services to plan to cancel. The first choice should always be to cancel the West Ealing to Greenford service and arrange ticket acceptance with London Buses (which provide a much superior service to the vast majority of potential passengers in any event on that utter basket case of a line). The second choice should be to cancel the diagram that includes the 0742 Oxford to Paddington, which has a Marylebone train one minute behind it and another fast Paddington train 11 minutes later – this is exactly the commuter market that has collapsed due to WFH▸ .
Those services have been identified with more in mind than just which impact on passengers the least.
Other considerations include how well staffed the depot that works a particular train is, what the crew do before and after, and what the train does before and after. I guess it could be optimised more given time, but there wasn't much time in which to draw up this plan.
Greenford services are crewed by Paddington
GWR▸ drivers (the former
LTV▸ depot) and if you look at what other routes those drivers sign there are hardly any other cancellations they could possibly cover anyway, as the former LTV depots are in the best shape of all in terms of being able to cover the current shortages.
Taking your 07:42 Oxford to Paddington service. That train is formed off a diagram that stables at Oxford overnight, which has previously done a quick trip to Didcot at 05:40. You could probably justify cancelling that Didcot run as well as the 07:42 to Paddington, but what do you do with the set that has stabled overnight? It then goes on to form the 08:50 Paddington to Great Malvern. I suppose you could look at starting that at Oxford with the stabled set, but then you would have to find a driver to bring it out of the sidings for it. Also the Train Manager (and Customer Hosts) both work it from Paddington to Great Malvern, so you would have to find a way of getting them on another train to Oxford (which might not be possible due to breaks) or find another Train Manager from somewhere.
It's not easy.