I'd like to assign a button on the D750 to switch between AFC-3D and AFC-S. Can this be done? Or maybe I can assign AFC-S to one button and when I click on it 2 times it goes back to the previous AF mode. I would actually like to assign this to the AE-L/AF-L button. These are the two AF modes that I use the most and I'd like that switching between them could be a one button touch operation.

I'd also like to assign turning the AF assist light ON and OFF to some button if possible.