I would say that the V7 gets it's power from the flatted fifth interval, aka the tritone, aka the most dissonant interval this side of a minor second. And like you say, it can be understood in terms of voice leading, e.g.the 7th (the "leading tone"!) "wants" to resolve up to the tonic.
It's interesting that you mentioned motif because I think that fits well with what I was saying about the length of the pieces. Seems to me that one isn't going to have much room to develop motifs unless writing in an extended form. But for me personally, this doesn't seem like a good requirement for a piece to be satisfying in the way that I think we are talking about. If you are seeking that kind of intricacy from modern music, have you checked out Bela Fleck & the Flecktones? Also, have you explored Zappa at all?