This year I experimented with a soft-sided cooler as part of the food pack.  We packed it completely full with our steaks (the one thing that we really wanted the cooler for) and stuffed the rest of it with our salami, bacon, and jerky.  Those other items didn't really need to be frozen at all, but we used them in place of ice.

All the stuff went into the freezer at home pre-trip packed in the soft-sided cooler with the steaks surrounded on all sides by the other items.  We pulled the cooler out of the freezer and zipped it up to put in the food pack the night before we left.  Once we got to the outfitters, we asked to store the cooler (with the top open) in their freezer.  The next morning, we got our cooler out, zipped it up, and placed it in the food pack.  The plan was to have steak that night.

I figured the steaks might still be soft-frozen when we hit camp and need an hour or so out on a rock to finish thawing.  We hit camp about 4:00, I checked the steaks and they were still frozen hard as a rock!  Only the stuff on the outer edges of the cooler was starting to thaw at all and even that was still pretty hard-frozen.  I quickly zipped shut the cooler and we had a quick conference.  We decided we still had time to catch dinner out of the lake and that the steaks would likely still be good for dinner on day #2.

Day #1 had been sunny and in the 70's and we'd taken no real precautions to keep the food pack out of the sun.  Day #2 was more like 80 degrees with strong sun.  Once again, no attempt was made to keep the food pack out of the sun all day.  We hit our next campsite late afternoon and I zipped open the cooler hoping the steaks would have survived.  Sure enough, the steaks were still soft-frozen, but at least we had time to thaw them before dinner.

That evening as we enjoyed our steak dinner deep in the Q, we theroized that we could have easily brought ice cream in for the 1st or 2nd night if it was buried in the middle of our cooler.  Now that would be a treat!  

Upon exiting, we stopped by a grocery store on the way back and saw they had freezer bag liners for coolers which were basically a foil bag to reflect heat out and cold in.  They might have allowed us to keep foods frozen even longer.  I intend to find out next year!  I'm not going so far as packing in gallons of milk and Frosted Flakes like some folks apparently do  :P but a little ice cream might be worth the effort.  Worst case scenario, we'd drink it like a shake.

I think this system probably works plenty well without the need to pack in ice or sawdust.