watershed or bust if you use down or might wrap. zip duffels are pretty good too but I use light drybags inside them just in case.
Firepan: use a steam table pan Allied Buying Corp CAST-2004 Steam Table Pan - 24 Gauge, Stainless Steel Full-Size, 4"H
permit compliant so long as you raise 'er off the ground. super light, last forever.
PVC poop tube works, but the Eco Safe Boom Box is way more comfy and handles 4 for a week. Eco-safe.net
the k-60 k-pump is an ideal lightweight river pump.
I love using a sawyer filter bottle, as I can bring a hang bag and rig it a gravity filter, as well as having on-demand drinking water from the river.
I don't like using hard boxes, peli cases, dry boxes etc in the ik as it's too easy to take yourself out. A watershed chatooga with some foam and reflectix makes a superior soft cooler anyway.
the biggest aspect is simplifying the gear list. otherwise, backpack gear and techniques adopt great to ELF IKing. I love ELF multidays because the water is so gorgeous at low flows. Illinois, SFS, Bruneau, selway, there are many great trips that are excellent off-peak in an IK.
Do build a solid repair/rescue kit. Base it around tear aid, your throwbag, and just a couple biners/pulleys.