For the record, commercial SFTP server implementations seem to be holding back on ACLs and other SFTP features because there's no client support. There seems to be a chicken-or-the-egg thing going on here and it has been for a couple years at least. Someone needs to take the first leap, and my guess is it's not going to be the commercial vendors.
I'm aware of that. But it is hard to implement anything when I do not have a server to test it against. While most server vendors have client application as well, so they can test it.