Was thinkin the same.

If it is a 4pot system you want then maybe Wilwood or the likes or to keep it for some 2wd calipers.

Problem in fitting the Focus Rs calipers is that the radius means the pad will not have full contact on a smaller disc, not to mention the problems with fitting under a 14inch wheel.

For a simple upgrade maybe try the 280mm Fiesta St Brakes with the std Fiesta St calipers of a coswroth 2wd if they fit.