Thank you for your note.

I do not intend to try to modify SRFI 231.

My goal is to find a proper forum to discuss changes to SRFI 231 that I
consider to be needed for if/when I propose it for R7RS Large.

I do not want to make changes off in a (metaphorical) corner without the
possibility of other people expressing their opinions.  The question for
me is the proper forum for that discussion.

Perhaps it's this list, I don't know.

For now, I've made some initial changes to a branch of my own repository

https://github.com/gambiteer/srfi-231/tree/231-bis?tab=readme-ov-file

Not all instances of "SRFI 231" have yet been changed to "SRFI 231-bis".