Yeah all the same engine mods that can be done on the fiesta can be done to the focus as well but you would be far better off going for a 2.0 or st170 engine conversion tbh.

Brakes are a good starting point with st170 setup which rears are the same as rs and you need the st170 front hubs to upgrade to rs ones.

Looks wise most people either go for st170 looks or collection bodykit. If you want to splash out you can go for svt usa focus looks or rs looks.

Its really down to how much you want to spend tbh.