Just as an FYI, I'm currently working on an editor for the SE5 data files that should help a lot with modding. I'm starting with facilities, but plan to do most of the data files eventually. Progress has been very good so far and I expect to have a very rough alpha version done in another day or two.
Here's a screenshot of what the facilities editor screen looks like so far:
When I get the facilities editor done, I'll start on the components editor. I'm doing this in C# using .Net 1.1, so it should be pretty easy for most people to install and use. We'll see. I'll post more as I do more.