That's a very interesting route to take. Generally the facelift 156 does not have CAN buses like the 147/GT, so that makes some of the things possible.
1. I remember some projects where pre-facelift dashboards were swapped with facelifted ones. You will need to do some wiring job, and some of the functions may not work or are restricted, for example infocenter screen.
Having said that, it looks like the climate controls are standalone, so that it can still be retained.
2. You will need the engine ECU, matching codebox and immobilizer chips only. The locks are physical part that have nothing to do with the engine swap. The remote/alarm/central locking is again a separate unit and have nothing to do with the engine swap.
Regarding the brakes, the VDC function interfaces with the engine ECU, so with the engine change you will lose that function. The ABS block will have to be replaced.
Technically speaking, changing the size of the brakes may push the system out of the nominal operating parameters of the ABS, since the ABS is calibrated for that particular setup. However, it will not give an error and without actually measuring the performance of the system we will not know if it is operating optimally.
But as we all know, we like to have big brake kits and all that and as long as no error is shown we are happy
I think it is not going to be as straight forward as if you'd just swapped everything over. The challenge will be in interfacing the facelift-type harness with the pre-facelift equipments. Study the wiring diagram, takes a lot of time, but I think it can be done.