To share some more findings...
I'm rather intrigued by the evidence that the game is reaching out to a central server, in order to retreive a copy of the GameCore.ini file. Looking through DefaultEngine.ini, I found this bit of code:
XComGame.ini is commented out, but XComGameCore.ini is not. Googling turned up some more informaton regarding these settings.
This all implies that the game is capable of "calling home" to get another copy of XComGameCore.ini. I am presuming that this would override the values cooked into the .EXE file, giving the Devs further additional control over gameplay balance & ensuring fair MP play.
I think I'm going to go back and reinstall the demo. We know in the demo, that the actual GameCore.ini file was being used. I need to see how it is referenced/inherited in the other ini files. This might allow us to adjust the current ini files, to use the local copy instead of the cooked one.