Interestingly, a while ago I had an application where JavaScript was added later on in the game. The result was that we could split into two apps: a rich fast glitzy one and a basic one suitable for mobile devices.
I read an interesting analogy in an article (which I have since lost and so cannot give credit) about accessibility: Oxo, the kitchen tools company, started by designing tools for people with arthritis. Having designed tools with nice soft rubber grips and large handles, they discovered that non-arthritic people really liked the tools as well, and now Oxo is sold at your local Target (and they are probably raking in cash).