I don't have the Pac SWI-PS instructions in front of me, but yes, you can do that.
When you program the SWI-PS, you have 9 or 10 possibilities that can be outputted to the Z1. And you go through them and assign them to your steering wheel buttons. One of those is MEM (or maybe MEM + or something). But this will cycle through your presets. I can't remember which step in the programming it is. But you don't have to match your car's steering wheel controls to what they do.
I kept Vol up and down the same. My lincoln had a MEM button which I mapped to MEM up or Preset + or whatever SWI-PS calls it. I also had a MEDIA button on the steering wheel, I programmed it to be Track+ cause I wanted that instead.
As long as what you want to do is a possible output from the SWI-PS, you can program any steering wheel button to be anything outputtable from the SWI-PS.