Steve:
You could probably do this another way.
CVS lets you define "modules" using the file CVSROOT/modules. You can leave Chaco and company in CVS where they are now. Then, in the module for scipy, you include Chaco and friends (with the "&" syntax).
This gives you the ability to check out Chaco as a standalone module just as you do now, while also getting the same Chaco code when you check out scipy. The impact on CVS is minimal.
You are da man!!! I've just spent some quality time with the CVSROOT/modules file and believe I have been able to achieve a first cut at the project structure we are looking for without having to modify the repository contents in any way. Woot! It looks like we can probably just continue to tweak this file to further refine it as we go along. Many thanks!!! Dave Morrill