Oh, hell no!
Standardised API? Fair enough. Maybe even makes sense if it's actually achievable across all banks and building societies. Worldwide. Many banks are global after all.
Open source? OK, maybe. Enables the community to evaluate security, stability, interoperability etc.
Give 3rd party businesses access to account data? No no no no no no no no no.
And Fuck no!
Only a complete moron, or heavily bribed (and likely both) could ever believe this is a good idea.
Take what probably the majority of people expect, demand to be the most secure and private thing they do online, and open it up to every parasitic marketing twat out there. Fucking genius.