(Warning... i'm not sure if they announced that D3 will have a 2nd set of weapons like D2 had . if they only have one set of weapons then this idea will not work.)
I believe the weapon switch function was released with the expansion. It's been said that they do not currnently have the system in place for D3, but they might consider it.
I'm not really sure what you are suggesting here. Multiple weapon switch slots? Is that it? This is far from an original idea. It is pretty commonly done it D2. Do you know of any one that actually fights with a CTA? I also use a MF switch to an Ali Baba blade and Rhyme shield.