I think if I was doing that I'd mail a box with food to a ranger station not inside the wilderness like PP,  but like Dawson Trail and then you just fill up your current pack and dump your garbage and go. then you're at least not hauling an extra empty pack around. 

You might be able to grab a shower and a meal there too. (This is all said by me never having been to Dawson Trail so take it for what its worth)