If we move to a four-day week as standard I hope we do it in a flexible way, so that some people don't work Monday, some people don't work Tuesday, etc.

I acknowledge that could be difficult to manage in some industries (e.g. trying to get eight people together in a meeting), but it means that traffic would be lowered each working day, as well as people being more spread out when attending leisure activities (i.e.not everyone goes to the beach on a Saturday).

Don’t agree with this at all. The advantage of a three day weekend is that the extra day gives you time to tie things up, wind down, and actually be able to enjoy both days of the weekend instead of that only being true of Sunday (the tail end of which is fudged up by having to prepare for Monday).

I do this where I work (in higher ed). I work 4 tens and have Wednesday off. It's like having a lot of two-day weeks with alternating 1- and 2-day weekends. Also, if I need a Friday or Monday off I can change which day I take off for that week. What sold me on it was "never work more than two days in a row unless you choose to".

I see a lot of criticism of the 10-hour days, but in a mixed environment I like it. With the hours I chose I have a 1 1/2 hour work time in the morning where most everyone else isn't in yet that is very productive for me. I also have an extra half-hour after the time most people leave to do the same. My work is more project oriented, but I still have inconvenient meetings with small windows for work throughout the normal work day.

An important part of this is to eliminate the idea that as a society we all need to have the same 2 weekend days off. (Which we don't anyway because a huge percentage of the population does work on weekends, just not most "professionals".)

Let my dentist's office be open 7 days a week, with some of them working M-Th and some working Thur-Sun and some working Sat-Tues etc. Maybe some of them mix it up and do M/T/Th/Fr or M/W/F/Su or whatever.

K-12 schools are the tough nut to crack in this scenario.

This is a fun move to pull for the reasons you stated but also because it surprises those who didn’t consider it as an option when selecting a schedule. Downside- we need long breaks to truly relax and calm down. Not much resetting you can do in a day but with three there’s more opportunity.

It probably wouldn't be practical for small companies, but what I'd really love would be a rotating third day off that moved between Monday, Wednesday, and Friday. I don't think it'd make sense to rotate through all days because having it on a Tuesday or Thursday would just be annoying to go back to work for one day before having another break day.

With a MWF rotation you'd get 4 on, 2 off, 2 on, 1 off, 2 on, 2 off, 4 off, repeat and having that four day weekend every three weeks would really open up weekend trips that require more travel.

Give us choice. I’ll take a long weekend over a midweek holiday any time.

But I might want to vary it from time to time. So, choice.

1) Friday or Monday are more likely to be days off anyway, so you’re asking (slightly) less by asking for one of those.

2) Lots of people really like having longer stretches off, as it opens more options for things you can do with the time off.

3) If kids are off school, even for a non-holiday (teacher in-service, say) it’s often a Friday, so that’s a nice day for parents to have off.

TL;DR there’s a pretty strong case for Friday and a somewhat less strong case for Monday. I expect employers and co-workers alike to prefer either of those over Wednesday.