I run 225/45-17 front and 255/40-17 rear on Michelin Pilot A/S in the winter with no rubbing. ET is 47 front and 50 rear.
I think it looks and handles fine with this setup.
This setup maintains the stock 25.0" tire radius for a 128i sport package, which comes with F 205/50-17 and R 225/45-17
I don't think you can go wider than 225 for a 17" wheel in the front without fender work. I run 235/40-18 front in the summer with ET 45 and it barely fits, but as Eddy pointed out previously, the 17" tire protrudes beyond the wheel and would hit the strut where the 18" would not.
I hope that helps, and good luck.