Actually, you don't need to replace TEC or which ever race your mod adds or modifies. Nor do you need to disable the RaceSelect Dialog either. There is a Window count number in the "RaceSelectDialog" window file.
TXT
backdropDimPercentage 0.90
backdropBrush "ICOGameLobbyScreenBackdrop"
titleOverlayBrush ""
size [1064 , 808]
contentRefArea [0, 0, 1064, 808]
titleRefArea [90, 40, 508, 30]
titleOverlayRefArea [0, 0, 693, 90]
numFactionWindows 3
Change that number to the number of races needed, of course there's your back end to it as well, but that is all you need to change in order to select any added 4th, 5th, etc. race.