Ideas:

Palette swaps for current egis. (green felfire ifrit? bloody red garuda? blueberry titan?)

Skins for current egis that makes them look more like mini-me versions of the proper primals.

Skins that change the 3 egis to one of the others we've fought so far. It would be cool if we could swap whatever egi to whatever task (tank, dps, ranged), but that'd be a lot of work, so I'll settle for just having an alternate for each (Like levi <-> titan, shiva <-> ifrit, ramuh <-> garuda) For these the attack effects would be changed to what's elementally appropriate.

Carbys, with an extra "ruby" red one for melee dps.