Long ago when I used to have a windows computer I had a dual boot configue with windows and linux. I also had then, VMware installed on my windows partition and with this program I was able to have it access the linux drive and it was able to run linux without me having a create a virtual drive. Will Parallels ever have this sort of functionality? where it would be able to access another OS which is installed on a seperate partition without having to create a "virtual drive".
Although not quite the same as what you are requesting, here is what I did. I originally installed WinXP on a virtual drive which was under ~/parallels-vm running Suse 10.0 as host OS. I then decided I wanted a separate partition, so I resized my ReiserFS /home partition (hda3), and created a new Reiser FS partition (hda5) with a mount point of /WinXP. I had to change the permissions so that users could read/write to the partition. Then I cloned my virtual WinXP under ~/parallels-vm to the /WinXP mount point. It went fine and I now have my WinXP on a separate partition. (This could be another drive) From reading the documentation, I don't believe you can do this with an existing WinXP installation as as a dual boot as the drivers for the network, video, etc. are not appropriate.
What about doing it with hardware profiles? Someone suggested it elsewhere. Would be great if you could manage to describe how to merge your method with that approach for a complete solution