From what I've seen the manual and electric heating systems differ in a lot of ways, the control panel is only a small part of the system, for example the manual heater box would need all of the electrical motors fitted to in order for the controls to move the directional flaps. There's also the minefield of wiring those motors into the dash loom which melts my head even thinking about it.. Not saying it can't be done but whether it's worth the hassle is the big question mate!
Jay