I don't see anything wrong with putting the controller in the cab.
However, I've learned from direct experience that the wires going between the controller and the glow plugs need to be at a specific resistance. If it isn't, the controller will only cycle the glow plugs briefly...ever since this, I've been cycling the key on and off to get the glow plugs to cycle (I simply haven't had time to try installing a "proper" 7.3L glow plug wiring harness).
Here's a thread from way back when when I tried to make a custom harness for my glow plug system and learned just how sensitive the controller is to resistance in the line...
http://www.oilburners.net/threads/truck-is-off-the-drugs.10888/
If you can do it without modifying the wires to each bank of glow plugs, you should be golden
otherwise, I would be very careful to make sure that resistance readings are identical to the factory wires.