chris, if you're using the file on the SAK as a striker for the ferro rod, put a decent edge on it. I used a file and put a real basic edge on the bottom of the file. That way I can scrape my rod without worrying about the file folding closed. You don't need to put a cutting edge on it, just enough to get a good "bite" on the rod. You could also use that edge to scrape the magnesium bar and save your knife. I carry the Wenger SAK that's the same size in my multi-tool pouch; it's handy having the small blade and scissors, plus the toothpick and tweezers. That tiny knife covers the few tools my Gerber multi-tool doesn't have.
And the idea of a saw blade is a good one, too. I use a piece of hacksaw blade broken to whatever length is most convinient for the kit in question, and cover one end with a few wraps of duct tape for a "handle". As was pointed out, it's handy for trap parts and the like as well as for striking your ferro rod.
One of these days I need to buy some Sawz-all blades. I've never ried them but everybody seems to like them. I keep extra jigsaw blades in my Gerber pouch, to replace the one in the tool. It's handy having a saw that can cut such a wide variety or materials simply by changing the blade.