I think that the wider impact on parents and associated industries would be huge. There is already a mighty scrabble for holiday time amongst parents and this is not just for Johnny to jet off to the Canaries but just for a parent to spend some of the holiday at home with a parent and go on a day trip to the beach.
What I do think should be offered is much more support in area hubs for those children who are struggling either educationally or economically with a rolling programme of specialist teaching with SENCOs and budgets to fast track assessment and offer follow up support in the home school. Targeted careers support to help older dc focus on a career. Free lunches for those who need them. Day trips to local attractions and cultural visits.
The issues are not the holidays per se but the education inequalities that they bring out. One child goes and visits Greecian remains and reads all the signs, tries a different language etc. while another child plays on the x box all day with a weekly trip to McDonald's.
Of course that would all cost money to put in place and investment in training and staff willing and specialised to go with it.
Most of the countries I can think of have longer holidays than England. Are there countries with shorter holidays that do well on that model? How do children in those countries with longer holidays fare? What about those countries at the educational summit, what are their school structures like? I do agree though a half and half approach would not work and just annoys the parents.