I nursed till my kids were 16 months. I didn't introduce anything else to drink until then other then water. I didn't want to give them cow's milk then or ever. I created my own "drink" using rice milk with egg protein powder and a little "healthy" oil. (At the time I used olive oil but now I would use something like udo's oil or another source of omega oils)
I was making the same carbo/fat/protein ratio as breast milk. I also put powdered lactobacillus (good bacteria that is in breast milk) in it. My kids did great with it. A friend of mine whose daughter was adopted used it for formula since her daughter kept spitting up regular formula.
I chose not to use soy since it has estrogenic influences and I didn't want that for developing babies. I used commercial rice milk for ease but if I were introducing it at an earlier age (and had the time)now I might make make my own almond milk so there weren't other things put in it.
I have never given my children cow's milk and they are extremely healthy. My 12 1/2 year old has only missed 1 day of school due to illness in 7 1/2 years. My 7 year old hasn't missed any.