Okay, I dont fully understand what you're saying there so I'll just say what I would do.
You're on the right path about dummy spells. Try to use channel instead, it's entire purpose is being a dummy spell (it does sometimes not serve that purpose that well, but for this occasion it should be fine). Have one dummy spell for each aura. E.g. Dummy Devotion Aura is cast, add real devotion aura.
This would of course display the actual aura in the command card, which is not really a bad thing. It reminds people which auras they have on. It isnt very awkard. But if you wanted to fix that you would need a spell book for each aura. For each seperate spell book, add 1 aura and then disable all the spellbooks (but not the auras) for all players. Whenever you want to add an aura, just add it's spell book.
E.g. Dummy Devotion Aura is cast, add Spellbook devotion aura.
This will add devotion aura with out any icons. It means ofc that you will need 2 extra abilities per aura, so that's up to you to decide.