Not in the sense of a concentric set of levels, no. It's not necessarily
browser capability that's at issue; the user might disable any arbitrary
number of style hints. And even disregarding that, it seems to me that it'd
be near impossible to come up with a set of conformance levels that covered
all the platform-based combinations of capabilities -- that is, platform 1
might be able to do A but not B, while platform 2 can do B but not A. Or
am I missing what you're saying?
To take my original scenario as an example, the user might have said, "Don't
let the document override my background," thus disabling the use of both
back.image and back.color -- but the browser might happily display text in
the suggested color, rendering the page unreadable. Since you can't predict
what the user will allow a document to control, I think you need to be able
to group settings together into functional blocks.
-Steve