The only problem is that it isn't currently this way (despite what Google and Matt Cutt's might say). It is naive to think that this approach is going work.
Furthermore, you're competitors are going to do accessibility + SEO, and they are going to trounce you. randfish said this better than I could, so I'll leave it at that.
You can get away with what you are suggesting if you have staggeringly awesome content, but even then - why risk it. If you integrate SEO into your culture from the start, and have the right process then it doesn't have to be that hard.