Spiked Punch
Well, if the idea is to not change Spike's basic design, they could just make it so he figures out how to do something similar to what happened in SomE, but in a more positive way, and grow a little (like in this pic) while getting wings and remaining in control for a short time. Or maybe just do it one time accidentally and leaving him, the other characters and us wondering if he can ever learn to do it at will. Point being, the possibiity of his greed growth used a different way, with a different form.