It could be done for fields now by making an alternate clipboard map. Modify the existing map (a .bmp file) for the special events terrain by adding a field name with the field number. You don't have to name every field, but you could name the major ones related to the terrain. The field numbering system is still used in the background. Task Groups wouldn't work since they are in motion.
I think it's a good idea for historical special event maps, but I can't see it in the mythical world of Main Arena maps.