weirdly, looking it up, inset is actually one of the things people (specifically, box modeling people) would like it to do but it doesn't yet.  some people have written scripts that kind of do it (lots of limitations), and there's requests to add it to the modeling features.  some people are asking for it to be added to something called Bmesh.  i'm not familiar with it, but it seems to be part of one of those alternate distributions.  so i'm thinking it might be added in the near future, especially if people keep talking about it.

but it looks like there's no simple solution within Blender yet. people have mentioned Wings3d, which does.  i'm definitely not a Wings3D user (one of the many tools i tried and gave up), but i can probably figure out how to do edges there.  thanks!