Thanks Jim. One comment on what you wrote:
Avoid modifying MediaWiki core code LIKE THE PLAGUE (there, fixed that for you). If you find you can't do what you need to given existing hooks, either ask on a list like this one, or insert a new wfRunHooks() call and hook into it - then ask someone in the group to commit it for you.
I agree that one should avoid modifying the MW core code, but in practice, it can be done well, very robustly. I have been working with a modified codebase for over a year and MW upgrades are still trivial. I usually need ~15-30 minutes to merge the 2-3 modifications that don't merge automatically. And 30 minutes every 3 months is a good investment. In my upcoming MW book, I describe the method (but still warn in big letters not to modify the core code).
I do like your idea to ask the MW team to commit a few hook entry points.
DanB