Take a look at the
EQ2MAP Map Making Tutorial. The suggested way of making a starter (line-only) map is essentially what you're talking about... you use a small number of chat macros to tell the lines to start/stop and to add the vertexes. It's then parsed in a separate program to make the SVG file for Inkscape.
As for all the rest... we neither have the ability in the in-game UI do to on-the-fly updating and saving like that nor would it be worth the effort at this point in time. We can't make EQ2's UI act like EQ1's hard-coded mapping system. Plus, at this point SOE is providing the vast majority of the maps (even instance maps) meaning there's very little mapping left to be done anyway.