Andy,

 
>>Do you document anywhere exactly what features of the control support these guidelines?

http://cutesoft.net/developer+guide/Section-508-compliance.htm

>>Is it possible to enforce the guidelines by making certain attributes of tags mandatory rather than optional e.g. the alt attribute of an img tag or summary attribute of a table tag?

It makes sense. But the current version doesn't support this. We will add this suggestion into the next version.