it doesn't help but you can fit 8 inch wide rims if they are the correct off set without any issues, as i have 18s on at the moment that are 8 inch wide, but they are the correct off set for the mondeo.

the mondeo cossie look ones are around et40-42 iirc and are the cossie ones not et25 which means they already will sit abot 15mm further out any way.