>>34
Or it could send an file containing info about the files in the directory (xml would work nicely), so that the browser could display an index with an option to recursively download everything to a single container file.
automatically convert images to a different format when you rename their extensions
This is only a bad idea because filenames and filetypes are so stupidly mixed in most current filesystems. With a database filesystem, it could work (in an altered form). Although, of course, in a perfect world filetypes wouldn't matter, and if someone sent you a file of unknown type, your computer would request a filter or something (written for a simple VM with no system access) from that person to convert it to a base type.
E.g.: Computer receives image/png file, can't handle it, requests image/png->image/bitmap filter, receives it, user wants to view file, computer applies filter to file & displays bitmap.
Unfortunately, operating systems will suck for probably at least a couple more decades.