We did that once, lots of drum loops on a laptop and the guitarist triggered different parts with a midi foot switch. Some most of them were more Aphex Twin or Radiohead than straight U2 Coldplay christian rock beats.
It worked quite well for everyone singing as, well the rhythm was constant... but we had him and me, and I'm not awful and he's amazing musician. I fail to see how most people given a drum machine would struggle... or if they did they would soon get used to it. (would you hitting piezo's with your feet really be that much better?)
Would midi foot pedal triggering something electronic not be easier?