It can certainly be a palatable diet, the wide variety of vegetables can be kept. It will be hard to convince Asians to eat much less rice though.
that's an odd thing to focus on. Moving people off meat & cheese would do a whole hell of a lot more than moving people off rice.
There's also some interesting work being done on growing rice in brackish water which could turn some unarable land to arable.
Water is also not a problem, we are surprisingly good at treating water, can even turn saltwater into freshwater given sufficient energy.