Except you don't necessarily need GCSE maths and English - other things might qualify you instead. And you can get what you need as a stepping-stone when you need it - you do not necessarily need to work up to it over, say, nine years. Many EHErs take a GCSE after 6-8 months of work, so you don't get to the point where it is boringly repetitive.
One of the problems with the school system, IMHO, is that it suggests putting in place a bunch of knowledge just in case you need it later. This is a "bottom-up" attitude - if you collect enough bricks, you hope you'll be able to build something recognisable.
As autonomous educators, we have a "just-in-time" attitude - when we need to know something we go and find it out. If we want to get onto a course, we find out what qualifications are acceptable and work for the ones we need.
My point is that it is not necessary to impose lessons in X on a 5, 7, or 11 year old. They are bound to be interested in something, so you can do that and when they are 14, 15, 16, you can discuss what they want to do as an adult and work out how to get there.
My DD (18) will start on a law course at Exeter in Oct. She has NO A levels and only one IGCSE (Drama). Her academic quals for entry are 190 OU points, gained from five courses over 3.5 years. We started on the OU route by accident, almost, when my DD (then 14) came back from an exchange with so much German that GCSE would have been a waste of money. She did the level 1 OU maths course because it was more interesting and covered more than the GCSE. Also, by that time we knew she wanted to have enough qualifications for uni entrance, so she wanted to tick the 'GCSE maths' box (as that is the only mandatory qualification required for Law at Oxford...). She did ECDL this year simply because most places seem to want some proof that you have IT competence so we wanted to get a GCSE-level qualification in the easiest and cheapest way we could - 36 hours of personal ECDL study seemed more efficient than two years of GCSE.
My DS (16) has not decided what he wants to do but he is considering engineering. Over the past 2.5 years, he has studied for interest 60 OU points in a variety of science subjects and 30 points in maths. Because he does not know what he wants to do but it is likely to involve applying to uni, he has chosen to do an OU English course next year (to tick the English language box). We are also doing Russian, with a view to taking an exam next year, because it seems like a good idea for him to have a modern language and we've been doing Russian at a (very) low level over the last eight years.
None of this has involved a master plan - it has always been under discussion and the DC have always had the choice of whether or not to do courses. In fact, DS has decided that he will do another short course while waiting for the English course to start in February, so that he does not get out of the habit of working.