We're sort of talking about solving two different "problems."  The first, at least for me, is the best way to get my tarp guy line up and tensioned.  For that I have typically used a sliding hitch/taut-line hitch at one end and a trucker's hitch at the other.  Then, when I get the tarp on the line, I use a prussic at each end of the tarp (which I leave attached to the line) to keep it taut and aligned.  But at barely an ounze I figure I'll replace the trucker's hitch with one of those figure 9's and see if it makes things easier and faster or just adds one more thing to carry. 
The second problem is a system of tying the tarp down.  I have the same problem as Solo T which is getting all those damn lines in a tangle.  I use an Integral Designs Sil Tarp (which I love) and just stuff it back into it's bag, lines and all, when I'm done.  So the lines and tensioners just get into an unholy mess of tangles when its time to set it up again.  But I'll definitely give your idea a try, db, and see if that helps.