Yes you can, but you have to be very careful. It has to be machined on the swingarm side so as not to alter the spacial relationship between the caliper proper and the brake rotor. There is a limit as to how much it can be machined before the caliper body interferes with the swingarm, but 1/4" is doable.
Then you have to compensate by shimming the drive pulley an equal amount, as well as spacing the other side.
If you decide to do this find a good custom indy shop. It is not hard, but it is easy to make an expensive mistake. One of those "if you have to ask don't try this at home" things. It is also a good idea to recheck all the alignment parameters on the bike after you are done.