Mobowhuntr,
I think that the pack and/or bow idea as an anchor for the tag line is a good one. I use this particular rope and knot system for my fixed position stand and have a problem when climbing. If the tag line is not secured to something you can't slide the prusic knot up the rope. I have tied it to the tree, but just did not like it that way as it seemed to be too close to the tree and difficult to manage...probably just me, but I did not like it. With the pack and/or bow, you can place them a foot or so from the base of the tree and then use it as the haul line as you suggest. I believe that most packs (i know mine...since I carry so much crap ) would be heavy enough to hold it in place.
I plan to test this out...oh, lets see.....hmmmm, Friday.
Good Luck,
Craig