Well, here I am answering my own question...but perhaps someone more knowledgable can comment - I'm in pretty deep water here.
So, I created a macro as follows:
This creates a new viewport, which gets user input to pick points, center the plan in model space, and then for the scale of the viewport. It's assumed that the user has already loaded the base-plan xref. I was looking for a way to make scale entry simpler...putting in "1/48xp" for quarter scale isn't very intuitive.
^C^C_-vports \\mspace;z;c \;z;s \'_script
Then, I created a script for the user to run from within the macro:
This does the job of setting up the layers to print properly from within the viewport. It isn't perfect, and there's no error checking. Now I just have to create the other scripts (RCP, Demo, etc).
;This script creates a plan layer setup within a viewport
XREF RELOAD *BASE*
As for using variables in macros from my first post: the setenv command creates random variables...but I'm thinking my current route is probably the best. Comments?