Dynamic pseudo class cascade

Hi,
Is it a good idea that the dynamic pseudo classes work the way
they do in the cascade versus non-dynamic rules?

If an UA wanted to create a default style like:
a:focus {background-color: blue; color: white}
and then the author writes the style rule:
a {color: blue}
things wont cascade very well. If the UA tries to avoid the problem 
by using non-CSS features, the author cannot override them.

Perhaps this would work better if the dynamic pseudo classes sort of
cascaded by themselves, that is, an author had to explicitly override
the dynamic pseudo classes to overide such user agent rules? If so it
might be possible to reduce the restriction on how they need to be
written in correct order as well.

 /Staffan