As this really is a huge task, I would like to split it up between different developers. Taking over a few of these changes could be a nice way to get started with GNustep. If you are willing to work on this, I can provide you with all the details you need. Before somebody starts on this, we need to make sure that we have a copyright assignment from him/her, otherwise we would have to investigate each change to see if there was more involved than just copying.
This could be a good project for Google Summer of Code (deadline is on Monday, March 26). Students are encouraged to apply.