I build a couchDB webdav server back in the day, you could also edit json documents or file blobs directly. the problem i discovered was that all OSes totally staled their webdav support and there are also enough differences between oses to be annoying. In the end to build somthing with great performance you would also need to control the webdav client side and probably build a fuse webdav client. I would have loved to see webdav maturing and becoming what the 9P vision was just for the web, but this obviously never happened as all the applications just went into to the web and used rest intead of webdav and everything else moved to sync protocols that sync to local folders.