After thinking more about internal prescription lenses mounted in the Vive's lenses, the more I realize that the solution is more trouble than it's worth. Considering sharing the headset with another person would necessitate removal of the lenses, the design would have to facilitate quick and easy removal while at the same time remaining secure when in use. Contacts side step this issue, but I have thought about a possible solution for using glasses without risking scratching the Vive's lenses for the times I'm too lazy to put in contacts: bumpers.
Given that the closest eye relief distance on the Vive is rather glasses friendly aside from the potential of scratching its lenses, all that's needed is a way to keep that from happening. To do it, create a lens attachment that stays on there 24/7 and comes out to the side and away from the lens. Either design it to hit the edge of the glasses frame, or line the protruding edge with microfiber cloth and have it interact with the actual lenses of the glasses. It would never interfere with non-glasses users as the eyes/face don't come that far into the headset, and would allow people that use glasses to wear it without worry. It also would cost a next to nothing as it doesn't require another set of prescription lenses.