I'm not sure how this would work seeing that powering this would often activate whatever device you are rotating. At least if you hard power it, soft power wouldn't have this problem.
Other than the difficulty of use I don't see why not add this. The options of rotation I think should be based off how it's facing. Vertical rotation if horizonal to block and horizonal rotation if placed vertically.
BTW you can rotate rails by using redstone already.
Good Idea! Can be instantly used to rotate blocks, so to make roller coaster rides, elytra flights and more Very interesting by rotating gates, blocks, tracks and more. But doesn't look that reasonable, but still 93% Support.