It was studied and turned down for several reasons:
yards not set up (spacing)for locomotive hauled equipment.
single power source with no redundancy.
slow acceleration compared to MU's.
traction problems in slippery conditions.
power problems with single unit pickup in GCT.
shops and work force already set up for MU operations.
the choice to forgo locomotive hauled trains was made several months ago. read minutes of a few months back at: