Its simple, just "rice" it in a food processor. Just throw the florets and chop them up until they are the size of rice. This freezes well. I've made alot to freeze, just so I would have fast rice to cook.
I want that chinese food white rice taste to go with some of my dishes, and i toss a bit of vinegar in with the rice in the pan and lightly salt. Its good. its so versatile. The only downfall is that it doesn't "absorb" some juices the same way that a true starch would, so if there are dishes where the rice is required to absorb some of the moisture, it may not work as well.
As to cauli-mash, it took me a while to master a palatable mash. The food processor was the biggest requirement. I agree, cauliflower mash does taste different and not exact same texture. But I've loaded them up with so much ghee and seasonings that i traditionally put in regular potatoes, the taste is very close. I remember how bad my first attempt was compared to now and its a world of difference.