I have started looking into the parts and work required for said conversion. Its not for me, but for my friend who has an 07 WRX wagon, but wants the sedan look wider fenders basically). I have told him about the difference in width with axles and all. We know we need the fenders, bumpers, probably tail lights. Just wonderingif anyone knows of this being done, maybe help us out with it best you can. I love this site and he help and information it provides. Im trying to convince him to do this, but Im stuck with researching it for him right now. Thanks for all the help everyone
I have seen a few similar surgeries in Audi world. The RS4 wagons have the wider fenders front and rear, but they are not sold in the US. We got an S4 wagon but it was standard width. People bought OEM RS4 fenders, bumpers, and rear door skins. There was some cutting and welding on the rear to attach the new fenders, behind the door, door skins have to be removed and RS4 skins tacked on, but the front bolted right up. I'll see if I can link you to one of the build ups. I know its not a subie, but a very similar project. Audi conversion didnt require axle swaps though. He might just want to go with wider rim/tire combo to fill the gap if front suspension and steering permits. This sounds interesting. Let me find you a link.
EDIT: I found the links to the Audi build. Check out how/where they cut the rear panel right below the rear window. I know is an Audi, but maybe this will give you an idea on the rear section.