Well, I did finish the first stage of the tech tree renovation: scrubbing out all of the old techs and hunting down every reference to them in other XML and python files.
The XML was a pain, because the references are everywhere. Got it done, though. The python was easier, because most of the references can stay in for now -- they don't break the game if they still refer to old techs, they just return a void for whatever function is calling for that string. I can live with that for now!
I now have a new tech tree in-game that consists of a single tech: Dungeon Lore. (More importantly, it is possible to start the game without any XML errors.)
My next step will be to add in the rest of the techs in the framework. Then I'll start hanging the functions and dodads onto the new techs.
Sorry -- no screenies or teaser video clips at this point. This type of mod work is pretty boring and not very photogenic, but needs to be done. When I have a nice tech tree done, I'll post a screenie of that!