Even though they wouldn't come cheap, I bet your heatsinks would be a popular item. I'd add some of the commonly used film caps too, like the 0.1uF/1000V and 0.22uF/1000V. The later are a little harder to get a hold of. Maybe even some of the larger 680uF/450V aluminum caps. They aren't super cheap on Mouser/Digikey, and I'm sure you could get a much better price in bulk.
Great idea Justin, and much appreciated by us DIYers!