Make all files in a directory accessible to a group
See this answer to a slightly different question:
From what I understand, you want everyone in the users group to have write access to the data directory. That's accomplished by the following:
setfacl -Rm g:users:rwX,d:g:users:rwX data/
I hope this will persist across user sessions & reboots?
I started with this article, but bindfs proved to be limited and ultimately impossible to implement on my debian server with remote folder access.
Sorry, I don't remember the details anymore.