I was wondering what size the brakes are and what the smallest size rim would fit. If you were to seriously think about this car running in ASP for autocrossing this is going to be a performance advantage to get something wider on it.
Basically all of the above. The main consideration will probably be finding R-compound tires that fit (particularly in the front), and then choose wheel size accordingly. I guess running a smaller tire could also help the clearing prolems, maybe allowing to run wider tires? Reducing the overall diameter of the tire also lowers the car, reducing weight transfer, without any negative influence on suspension geometry.