It's not exactly easy to make an "accessible" DAW. Especially not when you consider that there probably isn't a huge market of blind music producers relative to the amount of work it would take to, say, make a somewhat-sane interface for a screen reader for a program as complex as ableton. The interface is very complex as is, and would almost certainly require some re-jiggering before it would work well. I doubt enough people would buy t to ever make it a worth-while investment.
I just did an interview with a (blind) professor from Berklee that run an assistive music technology program and lab that has been using Pro Tools for quite some time. He's released a pile of scripts called "Flo Tools"[0] to assist with visually impaired use.
Perhaps the reason to make it accessible is not because of market share. It turns out that other audio and (yes, even video!) mixing software is accessible, so it's certainly not insurmountable.
It is possible to map most controls in a DAW via MIDI and possibly provide a touch interface, or more tactile controls (sliders and knobs). Live looping for example, only requires a few foot switches.