I figuring making a real overlay map like what was featured in Dark Forces/JediKnight/MotS would probably be too much work, but how about this?
Force Seeing enhanced radar for SP/FFA as an option?
Ie: the way it is now Radar only works in team games and shows your allies within a certain radius as green arrows.
Make it so that enemies show up as red arrows if you are using Force Seeing.
Perhaps different levels of force seeing reveal more (like say mines or something) much like how it worked in JK/MotS, but using the Radar.
That and make it so you can use a key to "zoom in/out" with the Radar (ie: the radar would show more or less of the map as you zoom out, thus you could use it to keep track of allies/enemies elsewhere than just in the immediate vicinity).
If this isn't to your liking, there's always multiple screens to show different kinds of data, or making Force Seeing highlight other things like it does in SP.