How about either a reciprocating saw or jigsaw blade, both are small and a bit thicker than a hacksaw blade to they don't bend as easily (I do have a mini hacksaw in a couple of my kits, Ace/Truevalue hardware has a UA made plastic $5 lightweight handle that the hacksawblade slides into and 1/2 sticks out, very nice, but hacksaw blades do bend quite easily as they are intended to be used under tension by the ends)
I hadn't thought about the buttons. I've started including my clothing in my thoughts about EDC gear and have started standardizing on a few items in an almost uniform like fashion so I only have a couple types of buttons.
I don't have any altoid tins. I have tried some from co-workers and have found that they all have sugar substitutes which give me a bad headache (diet cola/pop does the same). So I've had to build my kit around something else.