It would be nice to have a command-line tool to convert back and forth between fruit:resource=file and fruit:resource=xattr. Using two shares with different options for separate folders and making a copy of all files is not an option since there is too much data.
I have a lot of old type 1 fonts and they don't seem to work when fruit:resource=xattr is turned on, which makes me think Samba won't read the AppleDouble file at all with resource=xattr. Looking at the source code seems to confirm this.
The files were initially copied back when there was a spelling error in fruit:resource (with 2 s). By the time it was noticed a year later, it was too late and there were several terabytes of data using AppleDouble files instead of ZFS xattrs.
Oh yes, I would welcome patches that implement this and will happily review. It shoudln't be too difficult for someone with basic C skills. Take a look at source3/utils/mvxattr.c for an example of a tool that does something similar.
Please note that fruit:resource=xattr only really works on Solaris (and derivates) and on FreeBSD.