merging unrelated repositories

[Jürgen Link]

  Hi all,
I merged several repos into one as described in 
http://mercurial.selenic.com/wiki/MergingUnrelatedRepositories under the 
title "Renaming".
This works fine, but AFAICS only merges the default branch (or more 
precisely, the branch which holds the current tip).
Is there a smart solution to also merge older branches?
This task is not trivial because the subdirectory only lives on the most 
recent changeset.
When updating to a previous branch, the original flat directory 
structure is re-established.
What I miss is a way to shift the creation of the subdirectory "back in 
time" (ideally, to changeset no. 0).
Can anyone help me out?

Cheers
Jürgen