I spent a week doing a refactor of a bunch of stuff. If you like that nerd stuff you can read about it here.
The general reason was that now we have tools in c# there are a lot of things that needed re-organising to allow more synergy.
Another thing we started to do was move the first person shooter stuff out of the base addon. I don't think our base engine should be providing that stuff. We should be trying to make the engine genre agnostic.
This worked out pretty good, and I was happy to see that the engine version stuff I built a while ago kicked in and hid all the incompatible addons until they were updated.