there is no way to create a list of all "enemies" in combat with your group - as there is no way to use SecureActionButtons with Enemy names (npc atleast i know) & creating/changing them in-combat
meaning i.e.
Code:
...
SetAttribute("target","unit")
SetAttribute("unit","The Lich King")
...
should not work
only way is Target-of-target but you would need all players for this ... -> lots of unneeded bars
(dunno if all right - but that's how far i expierenced it with LUA/API)