First of all, dealing with the issues in general (this isn't just school's responsibility but government, parents, other social institutions etc), so let's be honest, kids are being vapes to each other all the time, during and away from school, not just the toliets. Though on that, I think the home and government have the biggest role. More schools should get those vape and smoke detectors (yes funding should be provided), though I already know scholls many years ago having these. They are specific to the toliet it's happening in and alert staff.
The area of the toliet for sinks etc, should either be one in the toliet room (which should just be individual, not cubicles with weak doors) or that area should be completely open. That way hopefully people can hear if any nonsense starts.
Period passes should be automatic, I've know many schools to do this (and in my experience my lovely head of year on her own). She never had a problem once with it, in 3 years when she did it. 1. Girls had to come to her (though she was lovely so nobody minded), you could do this in the morning or lunch etc, and tell her. She'd then write a note in our planners, with our names and the date (so the whole week), and because she gave them to us, obviously you couldn't come more than once a month. Even if this was extended to a few different teachers, it could still work well - if logged on a wider system. She'd also sign it.
The other issues such as bullying, as I said earlier, banning toilet use isn't stopping that problem - just stoping it happening in one place. Bullying still happens when staff are around, and it's symptomatic of a wider issue. Again with knife crime, that's a whole separate issue, about SS, families with no support system until it gets to late, adultifcaiton and systemic racism in society and school safeguarding processes, poor youth offending support etc. But a kid will still pull out a knife and unfortunately we've seen those incidents to teachers as well (perhaps more metal detectors are needed, I know some academies etc which have these).
On vandalism - that's probably the biggest issue which banning toliet use helps (as for the others it just puts a band aid on the problem). I think it comes from respect and sort of pride in your school. School environments have become about conformity, stripping away student identity and anything which relates to them in the curriculum and overly strict policies on things which have no difference to learning. Kids have always hated school yes. But schools right now aren't safe spaces for kids, they don't feel it's mutual respect anymore, they don't feel part of something (I think especially in massive MATs where everything is copied and pasted and teachers can't adapt things to the school population). Why wouldn't they rebel and break school property. This obviously is a hard issue to deal with, and obviously vandalism costs a lot, and that money can't go elsewhere. But I think having open areas of the sink etc and CCTV there can help (not in the actual toliets but anywhere before it). Trying systems like having more toliets in general and where possible next to offices.
I know some schools have like pastoral teams (non-teaching) and have put the toliets there, and because the office is see-through with glass, all the staff (including lots of admin staff etc who can alert SLT duty) can see straight through, to the biggest boys toliet. Again they have done this with as many toliets as possible and the threat of staff seeing has helped. But they haven't had to ban toliet use, the policy is basically unless you really suspect they're up to something let them go (rare these days I know), some kids still have medical cards but staff know and that just happens with a nod or something. It's one at a time, and it's logged if they spend too long.
Is this all perfect, no, but I do think where possible some of this is workable or should be implemented when schools can (with more money etc). Another great idea I saw, was the card system with an electronic strong lock, however would cost a lot and obviously not possible right now. But ideally would be the solution. I was thinking for disabled toliets there's a radar key (for some not all) and most disabled people buy one and it unlocks those specific toliets. A system like that could work and maybe one key per classroom, teacher gives it out and they come back and hand it in. That saves all the long walking to the office - more chances for long bored walks back and seeing a friend and disrupting a lesson. That would require obviously all toliets to be individual and changed, so not a right now solution, more idealistic.
The incident someone said where a girl was jumped, quick question. Were all the kids in the same class? If so why were so many let out at once. If not were they waiting for her? Like they all asked, but how did they know she was going there then - or did they message on phones during lesson? It's much easier to do it on the playground or out of school, in my experience.