I think having optional stuff, like free staff yoga once a week, that people can do if they want to, but no pressure to join in, can work well.
Anything that's compulsory before/after school is just more stress.
I, personally, hate before school meetings. Morning briefing once a week I can cope with, but 8-8.30 meetings before school stress me out and I'm always just thinking about all the things I've got to squeeze into the day!
Centralized detentions are really good, as long as there is someone in charge of chasing up attendance- it's pretty demoralizing to set detentions knowing they probably won't be sat, and no-one will do anything about it.
Consider how many duties staff are doing and when. If staff get a free meal for doing duties, don't penny pinch over this!
One thing that would be (relatively) easy to implement, and would make a difference to my quality of life is allowing tutors to have tutor time in their own teaching rooms. It means I'm not running across school to get to my first lesson, I can welcome kids in the morning more easily, as a science teacher I can set up practicals in advance, and I don't have other people's random stuff left in my room. I can't see the need to have e.g. all Y11 in the science corridor, all Y7 in maths and so on.