I am the manager of the WHS group on Linkedin, so I get to keep up with WHS and all of it's variations ( including Vail).
I am glad this is not just for WHS, as the Drive Extender has been discontinued, and will be replaced with some form of raid. WHS V1 will be discontinued in a few years. This has thrown the WHS community into disarray, so if the tv4home can work on Win7, much better. Please keep the original WHS addin going,
V1 is not dead yet, and would make an excellent platform for this project.