I have a fair bit of experience switching between booting a Windows partition natively and running it as a VM. First of all, hardware and driver support were NOT an issue for me, nor was it necessary to uninstall VMware Tools when booting in a physical context.
That aside, it sounds like a great idea, but product activation is where it really falls down. One is not supposed to have to reactivate Windows every time Windows switches between P and V, but it is not foolproof. Windows and Office both will occasionally ask to be re-activated due to alleged hardware changes. Once, after switching between physical and virtual modes, my properly licensed installation of Windows 7 deactivated itself with a bit of fanfare due to an alleged "activation exploit." These issues would be avoided, or at least rendered trivial, if they occurred in a KMS environment.
When I upgraded to a 300GB SSD, I brought my Windows partition over as a VMDK and never booted it natively again. Windows 7 seems to perform better virtualized on an SSD than natively on an HDD, and the sparse image that I use now consumes less disk space than the old partition.
Executive Summary: Yes, it can be done; drivers are less of a problem than you expect, and Windows activation is more of a problem than you expect. If you don't really need to run Windows on bare metal, I'd suggest converting your partition to a VHD or VMDK and running it only as a VM.