I have a UK spec Focus mk3.5 (April 2016) 1.0 ecoboost. I bought a second hand steering wheel with the cc buttons and then followed the fitting cruise to a mk3 instructions.
Only thing I didn't do was to update the IPC (as the Focccus 0.8.6 software didn't allow it and info above suggests that it's desirable but not necessary). All worked fine and was very straight forward. The pictures of the airbag release mechanism above even made that bit simple.
All the cruise and limiter buttons work and dash lights too.
So, it can definitely be done, but perhaps there's a nuance with the model types or the steering wheels? I was careful to buy a steering wheel from a 1.0 ecoboost just on the off-chance.
Happy to supply further info if it would help. Thanks to previous posters for all their info and sage advice.