Machining the wheels will seriously reduce the strength of the wheel and put more undue force onto the lugs, which could in extreme circumstances snap.
As for pulling the arch lip out, this may be the solution but be aware tat the inner sill is rather stong and you may deform it, which may cause more hassle.
I was told of a drastic way to do it, but this is so drastic that it hurts just thinking about it, involves saws and welding..... nuff said.
Apparently so Ive been told, so dunno if its true, but you can get tyres that curve inwards berfore the tread, kinda like a flatened trianle, know what I mean? So u could get a 225, but the tread is only 215 wide.... dont ask me where u get em from though.
Hope this helps, should see mine it looks like a dune buggy !!! They stick out about 1 inch!!!!
Si