Enforce writeable on filesystem

Hi guys,
we have a data transfer network drive, shared via nfs and samba.
But now I got the special demand to make any of the files read and wirteable, regardsless of the permissions they had before.
With acl I get the right permissions (via default values) but the standard unix permissions overwrite this. (e.g. when I have 644, it does not care that the group has write permissions)

Does someone have an idea (except chmod via cronjob :wink: )

Best regards,