http://www.w3.org/TR/xhtml2/mod-structural.html#sec_8.10 . lists
block@kind as an open issue.  I'm not sure anyone is entirely
comfortable with the kind attribute representing the actual semantic
value.

How about adding a structure attribute, perhaps even to the core
attributes?  (What we really want is "conceptual size", but size
*will* be used for styling.)

Then, instead of

    <block kind=samp>...

Users would write

    <samp structure=block>...

If there are too many concerns about letting the content model depend
on an attribute, then I would suggest adding a block element to the
Text content set, so that people could write

    <samp><block><p>now you can use more than inline --
                                     because it isn't a direct
descendent of samp.
    </p></block></samp>

-jJ