My primary issue at the moment is the inability to create a bootable external drive. If that can't be worked out, clones per. se. are almost useless.
I thought Mike Bombich of Carbon Copy Cloner fame has said that indeed, the only way (for now) to create a bootable external drive, was to use Apple's Installer first
to install the OS on the external drive then use CCC to clone the Data volume. Clunky but bootable. You as much said this in your fifth bullet point above.