In reply to Rafa Poveda.

If you end up creating the theme, I'd encourage you to blog about your experience. Talk about what you learned along the way, and how the experience changed you, etc. The accessibility community in general needs more designers and developers talking about accessibility in an open, honest way. More than anything else, in my opinion. :)

A few other seeds I'll plant:

Join the WordPress Accessibility team, we'd love to have you!

If you have patterns you use in the theme that you'd like to share, we'll take pull requests here: https://github.com/wpaccessibility/a11ythemepatterns It's a set of patterns for building accessible themes that the WordPress Accessibility team is leading.