I took lessons at one point from a jazz guitarist who used a thumb pick in collaboration his index and middle to pick which was pretty cool because some of the harmonics he could pull of with the thumb pick were phenomenal. It was too much of a change though, going from flat pick to thumb pick, and I couldn't hack it.

I'm pretty sure this arpeggio thing is straight forward - actually I think a portion of my riffs related to it back when I was pinkyless in my playing - but until I see someone doing it or get proper instruction on it, I'll let it be. Maybe the second half of my Rock Discipline video deals with arpeggios. I'll have to check.