A couple more details to share:
1. With the base cluster, the extra buttons on the steering wheel shown in the photo I posted above do nothing. I need to poke around Forscan when I've got more time to see if there is anything I can change to get the buttons to do something.
2. Earlier in this thread I questioned whether or not it would be possible to add the cruise control switch "pod" to my base steering wheel. After comparing steering wheels, I'm pretty certain that would be a big PITA. However, if you love a challenge, I'm sure it's possible, though you might need to break out the Dremel.
3. The steering wheel I used (from a 2014, not a 2015 as I said above) does not have the audio control buttons so I still don't know if I had those buttons whether or not they could control the base AM/FM radio.
Feel free to contact me with any questions on this fairly simple upgrade.