Thanks for your return, and link. I knew PyCQA but not the others.
It seems i didn't success to precise my idea correctly. I'm 100% OK with you that this is not language role to indicate precisely which tools to use.
But my idea is only to define basical metrics, useful to evaluate quality code, and related to PEPs if existing. I precise i'd like to propose informational PEP only. I'm not considering that my idea must be mlandatory, but only an indication to improve its code quality. So each developer/society would be free to evaluate each metrics with the way he/it want. As for PEP8 for example, for which each developer can use pep8, pylint, ...
The PEP257, for docstrings, indicate how to structure our docstring. My PEP, in my mind, would indicate how to basically evaluate our quality code, only which metrics are useful for that. But only this, no tools indication.
Customer i see regularly ask me for being PEP8 & 257 & ... "certified". This PEP could be opportunity to have opportunity saying be "PEPxxxx certified", so customers would be sure that several metrics, based on PEP and other parameter, would be use to gurantee their quality code.