Woot! I'm having a bit of a breakthrough here, but ran into a minor problem. Here's what I did. I created an empty folder on my desktop and then took my Pakfiles folder and put it in there. After placing the "Unpack_NFS_SHIFT.bat" (with the 2 corrisponding files) in the new folder and running it, guess what? EVERYTHING is unpacking for me as far as I can tell!
The only problem is this: Unpacking the Pakfiles folder results in the creation of an audio and a movies folder. There's already an Audio and Movies folder in the root of SHIFT. Now what? Just copy the contents of the newly created folders over to the folders in the root of SHIFT? Same name folders right? So when the game goes to look for a file in a folder labeled "movies" or "audio" it'll be fine? HELP! I'm so close I can taste it... mods of my own!
EDIT: Just noticed there's also a resulting gui and render folder as well. Crap this sucks!
EDIT 2: Well, I'm going to go through and only add newly created content from unpacking to the duplicate folders (and yes, sub-folders. even some files are replicated I've noticed) from the original install. I'm hoping for the best here and will post results as soon as I'm finished.
EDIT 3: Result = SUCCESS! Don't know why unpacking the Pakfiles folder on it's own worked, but it did. I did this with the patched version of the game by the way. Just needed to go through the various resulting duplicate folders, sub-folders and files and add whatever new content the unpacking process created. I did experience the slow game load time and track/race load time the first (and so far only) time around. I'm just happy I found a way to get things working for me. Thanks to those who offered up advice and tried to point me in the right direction, but I guess I found my own answer. Anyone else in the same boat as I was, try this method and see what happens.