My issue with stunning strike is that it is so much more effective than the other ki options that it turns monks into a one-trick pony. When you think of monks, you think of stunning strike. Maybe the answer is not to nerf it, but to give them a few more options that are competitive with it, to increase player choices. Mercy monk actually does this, which is why everyone (including me) is playing Mercy monks right now. More options equals more fun.
I actually think the monk chassis is pretty good - they do play differently than other classes, and they do feel like a highly mobile, light fighter. They're just a bit undertuned. They just need a bit more damage, a bit more survivability, and bit more ki, especially below level 5.