A Modified Front Subframe was used in the very heavily modified rear of the Mini.
Usually, no steering rack is fitted to the backend, but additional linkages are fitted to take the place of the steering rack and keep the Hubs pointing straight ahead.
As an aside, I'd just like to mention that one thing that keeps the Mini so stable on the road is that most of the weight is so far forward and IMO, with such a short wheel base, if the weigh was closer to 50/50, if the back were to 'come out. it swaps very fast.
I can totally agree with keeping the power train up front I used to own a Clio V6 for many years. Being a short wheel base car and mid engined, on the limit it gave you basically no warning and then would lose grip suddenly as I found out when pushing it hard on the track. My friend had a hayabusa mid engined Z Cars Mini. Brutal acceleration, but by having the engine in the middle it just totally destroyed the predictable handling of the car.
I find my current Mini with the engine up front to be so much more predictable (and fun) to drive than either of these aforementioned vehicles.