I'm not as familiar yet with Yii as I'd like to be, so please forgive me if this is already in place and thus a moot point…
I’d like to see Yii embrace the concept of Progressive Enhancement as much as possible. I work with a lot of US government sites, and all sites under the US Gov are required by law to support s508 whenever possible.
Making sites work properly in s508 under Prado has proven to be quite tricky. I thought that if action was taken at this early stage with Yii, that developing s508 sites with Yii might be a little more painless.