as you go down in rim size you will naturally go up in profile of the tire. this will naturally give you a greater volume of air in the tire and many benefits. benefits would be a softer more comfortable ride, lighter wheel and the tire will be lighter too, especially if its a lesser width. better gas mileage, drastically improved all wheather handling, tighter tuning radius, less wear and tear on you suspension components and less prone to tire bulges and rim damage from pot holes.
you will lose those i corner g forces though.
i just went through this dilemma. i just ordered a new sfe and just ordered new wheels and tires before i even recieved the car. i ordered the sfe for the all around disc brakes and cant stand the though of hub caps and the tires are know to be awful in the winter so i ordered mono winter 2 wheels and 205/65/15 tires. 94h speed and weight rating. the tire will stick out the same as the 215/55/16 since the wheel offset of 40 pushes it out 10mm over the 50mm stock and the height is actually slightly taller than the original. So you have many choices out there and if you still want a large diameter rim check out centerlines or team dynamics.