Yeah, I think that Wednesday will be the "peak" day.
For example, with the "new mums" at the place I work (a fairly ordinary office building where the vast vast majority of full time people were in the office for five days a week), some want to do the first three days of the working week, some want to do the middle three days of the working week, some want to do the final three days of the working week - which means Wednesday becomes busier than other days (going off topic, but my understanding from talking to people in this position is that two days a week often isn't sufficient to make it worth returning to work, given the corresponding loss in benefits).
So, if that's anything to go by then, even if the people returning to offices are doing a mixture of one/two/three/four/five days, I think Wednesday will be the busiest day of the week (and therefore various team meetings scheduled for Wednesday as it'll be the only time everyone is in at the same time)
That means we could be in a situation where a four coach EMU is sufficient for a London commuter TOC on a Monday, an eight coach required on a Tuesday, twelve coaches on a Wednesday, back to eight coaches on Thursday and four on a Friday - but infrastructure will have to be based around the once-a-week "peak" day, which may mean some units sat idle a lot of the week (compared to the way that recessions were in BR days, when passenger numbers nosedived, but at least stabilised to a fairly similar level of demand for the five days of the woking week).
We're obviously just speculating but I think that the talk of whether commuting levels go back to 30%/ 50%/ 70% of 2019 levels often ignores the fact that it's probably not going to be well balanced across the five working days of the week (but that the railway will be expected to cater for that kind of demand on the busiest day of the week, which may make the economies of ordering replacement stock a bit "interesting" - i.e. whether it's worth buying trains for just a couple of journeys a week).
BR were okay to have dozens of "mature" coaches sat idle most of the year, to be pressed into action on "seaside specials" and what not, but modern rolling stock doesn't work like that.