Well, I've got to throw a fly in your ointment, I'm afraid.

I love the idea. The big problem I see is that most people will be wanting to install a consumer printer for which WHS may not have a built in driver, and consumer printer driver packages are
notorious for containing huge amounts of bloatware and doing non-standard things during the installation process. So you won't have an easy way of controlling the installation. I've installed a couple of printers on my WHS, and getting one of them to install just the driver was a real struggle. I can't imagine an add-in that could control that process for any significant fraction of the printers that are available.