How to make creamy/starchy risotto with brown rice?
The "dissolved" starch is going to make a sauce or "gravy". Different sources of starch will have a somewhat different taste. So experiment a bit with different sources of starch and see which tastes best. You could even grind some of the brown rice in a mortar and pestle to get a brown rice flour that you could use for thickening. 

My experience with a risotto is that the rice is breaking down somewhat when it gets to the point where it is cooked. So to make a gravy I'd have some extra water/stock for the rice, and then add a small amount of a starch solution which would thicken when heated. You wouldn't want to start out with a starch solution since that would be easy to burn. You can't add a dry starch to a hot liquid or it will lump.