Your points one by one, gg2
*1. Holiday time both for students and staff to be reduced to six weeks. There should be no idea that teachers are expected to work in schools/colleges during this time.
2. There would be the equivalent of industry shut-downs for: two weeks at Christmas, one week at Easter, two weeks in the Summer.
3. One week could be taken at any time other than those exempted by the head teacher - these being different for different years where necessary.*
That would mean that every family with a schoolchild would want to take their summer holiday at the same time during those two weeks. As Gilly replied, the pressure on travel and accommodation would be enormous, like the traffic jams heading for the seaside on a sunny bank holiday and hotel prices (if you could find a room) would rise astronomically, so even more families would be trying to go during term time.
How convenient were industry shutdowns anyway?
*The day should be the equivalent to a working day with children arriving and taking part in non-academic activity. This would not include the academic staff who would have this time for preparation/marking.
The middle of the day would be teaching time. In secondary schools the subject/stage of learning could be introduced in lectures to the whole year and then smaller sets used to enable all levels of learning.
The last part of the day would not be academic and not include academic teachers in supervision or teaching but would be additional time for preparation/marking/training.*
There are already breakfast clubs, after-school clubs, and various initiatives to cope with children whose parents are work hours don't coincide with school ones. They all need one important element - adult supervision. Who will supervise? Teachers? Not if they are using the time for preparation and filling in endless forms. That means extra staff. Staff means training and money, and keeping a whiole school-full of (possibly unwilling) pupils occupied in non-academic activities takes a lot of space and equipment.