They require some form of Script to launch the Recovery Process and this is where things get difficult.
The Script and Base Files need to be located in a small Partition at the Root of the Boot Drive where as the Recovery Partition needs to be another Partition and the Work/Windows Partition is yet another. The Root and Recovery Partitions need to be setup prior to installing the OS where as the Windows Partition is setup from the Recovery Partition.
Copying things to the Root of the CD Drive means that they are read when the computer starts, well goes beyond the POST Part, the Root of the C Drive is the first thing that gets looked at once the POST Process is finished.
If you copy things to the Root of the C Drive you'll get a message something along the lines of [i] To Install Windows press any key[/i] much like you get the Prompt nowadays to Boot from an Optical Drive when it's the First in the Boot Order no matter if there is a Disc in it or not somethign like [i]Boot from CD/DVD.[/i]
The thing here is that to be Bootable the Root Partition need to be readable and not require software to allow the system to be able to read the HDD Data. NTFS Partition are not readable without the necessary software which is installed by default as you install Modern Windows, you are not asked if you want it or not it's just placed in there.
As for the drive plugged into the USB Dock it can not be bootable because the system doesn't read it as a first alternative even if you where to set it in the Drive Chain before the HDD in the computer you are using it's unlikely to be readable because USB Drivers are needed for a HDD where as a Thumb Drive doesn't need those drivers. If the Root Partition is readable by the Hardware it's by Default the Boot Drive.
I hope that explains things in a way that you understand though I think I've made a mess of trying to explain. ;)
Col