I am planning something similar with mine, but will probably go for 10x6 split rims.
It'll look similar to a miglia racer, but I think the sports pack arches will look too big. There is also a mod you can do on the rear arches to get it sitting nice and low.
Perhaps the best arches for a 10" wheeled Mini are the original works 'group 2' arches which carry the chrome trim over the wheel arches. Sprayed in body colour they look great. Classic image as well.