HMRC have been struggling to do similar with self employed/small businesses for about a decade now with their stupid "Making tax digital" for income tax, which has been postponed time and time again.
Originally, they wanted small businesses to use software for book-keeping which would "ping" all their transactions up to HMRC so HMRC could review their records. When HMRC finally accepted that wouldn't work, they downgraded their data requirements, and downgraded them again and again over the years. Now all they're wanting to be submitted are a small number of "totals", i.e. total sales for the period, total costs by category, etc., so basically, bugger all use as that's exactly the data they get from the self assessment tax return.
HMRC have so far wasted over £60m on the stupid scheme and still won't accept it's pointless and won't scrap it.
I think this proposal for access to personal bank accounts will go the same. Lots of hot air, ultimately downgraded and probably eventually forgotten about, but in the meantime, costing taxpayers tens of millions of pounds and lining the pockets of the HMRC advisory firms who are no doubt the ones pushing for it.
HMRC need to concentrate on doing what they're already allowed to do and doing it properly, before they even think of extending their powers/scope of operation. They're hopelessly managed and, at best, incompetent. New laws and extensions of their work will just make things work and make other aspects even more disfunctional.