If it is to be a survival rig how about using something like a SAK in place of the small thin fixed blade? If you chose the right SAK you would be carrying many other very useable tools(as well as a small thin blade) for a variety of situations you might find yourself in. One thing that SAKs also excel at is working on or helping to alter(think awl with sewing eye) your survival gear/clothing should you need to in order to adapt to the environment you are in. Something along the lines of a One-Hand Trekker or any number of the smaller 91mm multi-layered SAKs. I would also put a few Ranger bands around the sheath itself. They can come in very handy for lots of things and don't take up much space. Oh yeah, maybe a little extra paracord wrapped around somewhere.