a couple recent postings somewhat related .... one regarding the economic niche for certificates:
http://www.garlic.com/~lynn/2005e.html#62
another on the use of typical SSL domain name certificates in browswer operation
http://www.garlic.com/~lynn/2005f.html#9
part of an extended explanation about certification process
http://www.garlic.com/~lynn/2005e.html#45
http://www.garlic.com/~lynn/2005e.html#51
I see another problem. Even if the browsers would mark different quality CAs chromatically the users would have to understand this.
Try making a user understand there are different shades of "secure connection" when they have problems understanding the difference between "secure" and "insecure" in the first place.