For anyone who stumbles on this thread(it is pretty high in google search results):
For me it was annoying having to recast everything, so I wanted to do the same thing.
This won't be an exhaustive tutorial, just the high-level steps.
First, obviously you need the NWScript compiler.
The code for the powers is in "k_inc_force.nss". Use kotortool to get it. Syntax is C-like, so you can use any C syntax highlighting you want.
This is just an include file. The actual script called is listed in "spells.2da", impactscript column. This is what you will be compiling.
After making all changes to code you want, put the base script, and all includes it calls in a folder and compile. The result should be a .ncs and .ndb files. You only need the .ncs file.
Put the .ncs file in your Override.
These instructions are valid for for all games. Including Kotor 1/2 and even Neverwinter Nights (apart from any filename differences).
Misc note: Some force powers just apply poisons. Those are configurable in "poison.2da", not the script itself.
Misc note 2: If you want to preserve balance, you can adjust cost in "spells.2da" and damage appropriately.