Very nice write-up, some of it is foreign to me as I use a PC and Inkscape but the overall concepts look very sound.
My personal workflow for doing these is (so far, I could convert any time) to not use the snapmarks but simply index the sheet using a ruler along the side of my crumb tray.
If you have not seen it, I wrote up a way to semi-automate breaking up large plans for use in the 