Well, it is actually possible to do this right now, all the files that make up the UI are stored as text files under the \ui subfolder in MoI's main installation folder. If you edit those files you will be changing the UI, that's how some custom UI layout like the ones in these previous links have been done

Yeah Ive seen those threads before, but it's not exactly user-friendly aha.
I was thinking about drag'n'dropping panels around, saving different workspaces, that kind of stuff.

See these previous discussions for some examples of this using MoI's already existing scripting support

Also seen thoses, I think.
That raise another problem, a lot of threads get buried deep in the forum and nobody see them.
Kinda like that guy asking for Ship Hull advices. Why don't you use a regular forum engine with sticky posts and categories ?
I know you like this forum layout because you can see quickly the latest threads, but it's also possible with other forum engines to have a list of the most recent threads.

The problem is that scripting is in general a fairly sophisticated technical thing, and even with additional work to try and make it more accessible, it will still even at that point be out of the range of what many users will be able to understand how to leverage.

True, but the idea is to have the people who know how to script to share their scripts.
That's how user-created content work :) The end regular user just have to download those scripts and run them.