Why not have the Miche lockrings turned down to a smaller diameter? How much material would need to be removed? Also, it's much less hassle, and mechanically more efficient to ride with bigger ring/cog combos. The only reason 12t cogs came into existence was that you couldn't get an track ring bigger than 54t until maybe 10 years ago. Prior to that, it was an expensive custom endeavor to acquire said rings.