Great idea!
I did a similar mod to my Leatherman supertool 200 to add a hacksaw blade. I disassembled the tool and removed the thin washers between each blade. Then i took a cutdown hacksaw blade and ground and filed the tang side to match the profile of the leatherman tools and reassembled it into the handle with the other tools. It locks reasonable well in the open position, though not as securely as the machined tools.