I'm not fundamentally opposed to some sort of education reform, but this is utter drivel that can't possibly amount to anything.
I have no clue what the intention was with this other than being able to plaster the word 'British' over another doomed project (and I do cringe every time I have to write British Standard). This isn't going to be a vote-winner and it's practically impossible for Sunak to effect.
The ten year timeframe requires him to win two general elections - which won't happen; the cost of hiring new teachers will have to absorbed somehow and given how poorly funded schools are currently, it would require Rishi to pitch in with some of his wife's money; and the knock-on for universities as students' depth of knowledge decreases will require some sort of (costly) change and possibly even four year courses.
The IB already exists as something similar, but more concrete than the British Standard (the latter being more like RAAC) and A-levels aren't in all that dire a state. As much as I feel like the education system could do with a spot of change, even a succesfully delivered British Standard would probably only manage to be different rather than an improvement.
But Rishi must know that he has no hope of it going anywhere. Getting it up and running would just be spaffing money up the wall, and it's only his 'silver bullet' insofar as it would be a high cost solution where there are perfectly adequate alternatives.
An honorable mention for shortsightedness goes to calling it the British Standard when it would apply only to England.