This is very commonly done in full-scale, for structural reasons - the airfoil gets thicker at the inboard end, where bending moments are highest, to accomodate deeper, stronger spars, and thinner at the tip, to reduce drag. It is always used in combination with washout. The thinner airfoil at the tip will stall at a considerably lower angle of attack, so it must have a few degrees of washout to avoid tip stall and the adverse yaw that results.