Actually from what I can see the biggest hurdle at the moment is that Bioware compiled / compressed / encrypted the 2DA files. (I lean toward compiled personally, there seems to be too much plaintext remaining for encryption 'thou I'm hardly an expert on that subject and a couple of the files look like they may be both encrypted /and/ compiled.)
Those files control quite a bit. From feats and feat progression, to assigning what file goes to what appearance index number.
I've not tested the graphical tools or scripts from NWN at the moment, but the monster/item (UTI and UTC respectivly) templates seem to remain in the simple GFF format from NWN. (A GFF viewer/editor is available from the NWN Developers area.
You have to rename the file from UTI/UTC ect to GFF, and the tool itself isn't big on explaining unlabled fields but it's not bad.)
*EDIT* Just looked over the script files and they seem to still be presented in plain text. *shrug*
I'd personally guess that about 60-70% of the NWN tools will work on KOTOR, and a remaining 20% or so could probably be made to work with minor modifications. (It makes no sense for Bioware to signifigantly change a set of working file formats so I'm not surprised.)
Beyond the 2DA problems the next big kink in modding problems seems to be a map editor which is a much, much, harder problem to solve.
Oh, and personally I use the really old 'BifUnpacker'. ^_^