I have a couple of friends in different industries doing it. One is software, one is logistics. The logistics is condensed hours, and shifts, i.e. there is someone in every day of the week, and you move which day you have off accordingly. Clearly everyone wanted to go for friday or monday, though wednesday seemed popular. So that's a bit of a hassle, an it's also a 40hr week in 4 days which does make it relatively long days (for some people). The other is 100-80-100 rule. So not a 40hr week or 37.5hr week. literally 9-5 for 4 days, the caveat being that productivity needs to remain the same.
In the civil engineering/infrastructure world we're so backward that that wouldn't work, we're barely coping with innovation / digital tools as it is, let along HR matters such as this!
Furthermore, it would delay work, and especially if the supply chain can't fulfil the requirements.
I guess the alternative to this is to extend the statutory holiday entitlement so people have more time off.
Personally I'd love it, but I can't see it working for me or at least in my industry for the moment - society, business and so on is so tailored around the 9-5 (ish) world for 5+ days a week it would take a massive societal behavioural shift to enable it. Can it be done? Yes, but it will require significant effort.
Since WFH is not going to be a long term thing for the majority of industries it may well cause a bit of a shift in the sectors - some sectors can do 4 days some can't etc... but then I guess that gives you choices to change sectors and roles if that's the lifestyle you want.