Might the mechanism discussed in:

   http://www.roundup-tracker.org/cgi-bin/moin.cgi/UserMenu

be a workaround? Basically it uses a detector to generate
the html statically on user changes and defines a tal macro
that can just be substituted when the page is rendered.

So it takes the generation of the list by querying the database
out of the flow of displaying the page.

Not the best solution I agree but it is a basic caching
mechanism.