Looking out of my window and my neighbour has a mk1 Focus saloon. Back in the day, I remember the Orion 1.6i Ghia being thought of as a better handler than the XR3i due to the fixed rear window and the joining of the rear suspension turrets under the rear seat. I bet the Focus 4 door is even more stiff than the hatchbacks.

My 2p worth is, the 30kgs is the least of the ST170s problems, the fact it makes 155bhp on a good day and the long gearing need to be solved first. Also that heavy DMF, get that removed too