For me, personally, part time work would be the dream. I used to contract and would do year long projects and then take large multi month breaks between. Neither "mode" was optimal. Work periods are obviously stressful and its hard to find free time. But the rest periods also got a bit old after a month or so, and even when we were traveling to cool places, I would find myself grabbing the laptop and coding just for fun and to keep my skills sharp. A part time scenario seems like the perfect in between.

However, I never saw a place where it could work. For one, if the rest of your team was full time and you were part time, you would automatically be less productive and useful than the rest of your peers.

With your Monday / Friday scenario with no meetings, it seems like the people that only worked Tue - Thur would have their schedule disproportionally filled with meetings, and have much less time to get stuff done. This could work for a manager type role, but it wouldn't work for an IC.

I feel like part time work, much like remote work, might require an all-in buy in from the whole team. I wouldn't be surprised if in the future companies go "all part time" and have their whole organization be tuned for part time productivity.