[xsl] Help: amalgamate a series of consecutive mixed nodes

Within some XML that I am processing are structures like the following:

<list>
  <item>...</item>
  <item>...</item>
</list>
<indent>...</indent>
<list>
  <item>...</item>
</list>

This structure does not mirror the document structure very well, because
logically the <indent> element is part of the <list>; it's a follow on from
the immediately preceding <list>/<item> element. But the XML reflects the
document formatting rather than the content :-(

If the requirement was simply to handle a single <indent> which followed a
<list> then I could manage it quite easily, by having a special <item>
template for the last <item> in a <list> whose first following-sibling was
an <indent>, and a null template for an <indent> whose first
preceding-sibling was a <list>. However it's not quite as straight forward
as this, because where I have an <indent> in my example I could in fact have
a series of elements, e.g. a mixed sequence of <indent>, <Sindent>, <SBody>,
and others.

So what I am after is (I suppose) a special template for the last <item> in
a <list> which is followed by one or more siblings whose names match a list
of permitted "followers", and a null template for any of these followers
which have a <list> amongst their preceding siblings, and which only have
permitted "followers" between themselves and the nearest <list>.

I'm finding that difficult enough to specify in English, and it's certainly
beyond me in XSL. Has anyone solved this kind of structural problem before?

Thanks
Trevor