"[tag[tag[expression]]]" - why not?

[twgrp]

No problem to list all tiddlers with a certain tag:
<<list filter "[tag[acertaintag]]">>

But if I want to list all tiddlers with "tags of a certain tag type*
- i.e where different tags are themselves tagged with a certain tag
it seems logical that I should be able to use a nested command like:
<<list filter "[tag[tag[acertaintag]]]">>

Is there anything that can accomplish this?

I can also not make it work with MatchTagsPlugin[1] as is obvious
here;
<<list filter "[tag[<<matchTags "%0" " || " acertaintag>>]]">>
(the || is the separator in the resulting inner list, intended to work
as logic OR for the outer argument).

IF solved it would enable enable "semantic tagging" [2] and to use
tags for structured data, a much desired feature IMO.

Any thoughts? Also completely different ideas to solve it effectively
are welcome, of course. The above macros are of course extra
appealing as they are core macros and/or relatively compact to write.

:-)

[1] http://www.tiddlytools.com/#MatchTagsPlugin
[2] http://groups.google.com/group/tiddlywiki/browse_thread/thread/b501b9832122e775?hl=en