I do this alot these days, so here's what I do:
One thing not to do is mix too many fruits. 1 or at max 2 fruits because of the way the stomach digests sugars. Then, keep it simple, and definately only use fruits and stuff that are "in season" if you can, and the natural "mixes' are digested well, and the useful energy is not destroyed by other organs having to process lots of sugar.
recipe 1: 1 apple, 2 bananas, nuts, sprouts (lots of any type i like echelot sprouts, cinnamon powder, vanilla powder, and use tofu of whatever consistancy as a thickener.
recipe 2: carottes, potatoes, nuts, sprouts and hot peppers. Use any potatos, but I like baby potatoes and big giant carrots. Raisons and apples go well here too.
I add ice. Nuts: almonds, pine nuts, peanuts, walnuts ect. Experiment with powders, especially tasty peppers that do well with carrottes and raisons.
I also sometimes add cold pressed oils.
hope that adds a bit of spice to your great idea.