Not read all of this, but FWIW, I don't have huge amounts of sympathy with any hard line argument that its impossible to work full time with a NT 12 year old. I don't know if anyone here has taken this IMO pretty extreme view btw and I am hold my own views purely based on my own experience.
My 13 year old son, from the age of 11 along with many of his friends, spends an hour or two at home after school alone. Mainly he sleeps or watches TV after a busy day at school and early morning start. No problems at all so far.
Most of my son's friends go home from school by themselves, no parent pick ups. Depending on length of bus/train journey this can take some time as the average journey to and from a secondary school is longer than the average journey to primary school as there are far fewer secondary schools. So for instance, my son does not even arrive home till about 4.15pm on average - and often later.
Also, children at my son's school (and this is common I believe) can always stay on after school ends and go to homework club, the library, extracurricular clubs - this is all free of charge and it means again, they are being 'looked after' at school.
So IME the problem of after school childcare is not so hard to overcome.
As for holiday childcare, yes, this will cost money and IME older children and teenagers do not want to be left with childminders.
But where I live the local council and all sorts of private organisations run a huge range of full time daily holiday courses - sports, drama, or just general leisure and fun courses. These normally last between 9 - 4 ish. I don't know if I am lucky to have this choice or not, but I have never had a holiday course crisis. If one course is full, there is always another.
Again, it may be very possible for your child to get to and from the course venue under their own steam. If not, and you need to take them, this is not so good if you have a long working day, so yes, you'd need an understanding employer and some flexibility in hours.
But also I am ok about leaving my son, now 13 at home for a short day alone - not for a week but if for any reason the course was closed for a day, I am confident ds1 could safely fend for himself.
IME it is the holiday playclub arrangements that are the worst to overcome regarding full time work, but at least they are not a constant problem.
I totally agree that is is nice to 'be there' for your 12 year old every day after school and all through the holidays, and if your family set up allows you to be on hand, you are lucky.
But IMO and IME the argument that parental presence is totally necessary gets weaker and weaker as your child moves through secondary school.For some individual children having a parent at home is a really good idea but IMO not as a general rule.