We did the rice milk for awhile because dd was Milk Soy Protien Intollerant. I was also still bfing because I wanted her to get the extra fat (and she did love avocado's so that wasn't really an issue), so I would suggest continuing some formula for awhile as well.
And then, when she was basically over that around 14/15 months, we still mixed rice milk with the whole milk about 50/50--dd didn't like whole milk as much at first (rice milk tastes sweeter) and even though she wasn't showing the symptoms of the MSPI anymore, she did get nasty poops when we switched over. The dr. said that even when it isn't hurting them, many toddlers still can't digest everything in the milk and so their poops get runny and smelly--which does increase your chances of a rash, I guess. More than anything, I just didn't want to deal with the nasty diapers and I have a hard time beleiving that it isn't better for her if she had more solid poops. She was around 2 when we finally went completely with cow's milk and is totally fine with it now.
Good luck finding a combo that works--I know it can be hard to find what they will tolerate, both taste wise and physically
~Kim