I've decided to release some code that I had in the works for a long time. It's called HFL (which is short for Hacker's Function Library. I guess the name is inaccurate now as I have since changed my nickname to BlackBox).
In any case, it's a collection of extensions to the original Outpost2 API to let you do extra things with units, unit info, so on. It has some really basic GUI support code as well (for implementing custom command panes).
You can download it from:
http://blackbox.outpost2.net/HFL/HFL-0.7incomplete.zip (145 KB)
The library, (unfinished) manual, source code, etc. are all inside of that zip file. You have to make a couple modifications to your OP2 SDK headers (basically some changes to structures and a couple other things if I remember correctly; read readme.txt to see what you need to do to set it up).
The reason I am releasing it like this (incomplete) is because I don't have the time to work on it anymore. Anyone is welcome to modify it and post the modifications up (though it would be nice if you coordinated efforts via the forum, in case others are looking at making the same modifications that you are).
Hopefully though, someone has some use for it. If you have any questions about how to use it, I can try to answer them but I can't guarantee anything (it's been a long time since I looked at or dealt with some of that code).
Good luck and happy hacking!
-- BlackBox