A thought. Guitar strumming is not necessarily about the notes - it's as much percussion as anything else. Maybe think of it like a standard drum riff going "boom tick boom tick" alternating between bass drum and snare. A drummer can use just the bass drum for emphasis of a phrase (maybe in the turnaround or something), but otherwise there needs to be a basic rhythm which involves variation of tone. Think of it in that context, and other rhythmic ideas immediately come to mind (eg. "boom, tick, boom boom tick").

Graham.