What would the point of a Hilda Echo be? She has even less to differentiate her from her original than Grumpy Pit does.
You'd get a Zelda Echo, but that's about it.
Not sure if semi-clones are even on Sakurai's radar anymore, but I'd take Toon Zelda over Hilda any day. At least the size difference would help you feel like you're playing with a different character.
Idea!
Hilda as a Zelda Echo. All her specials are variations of Zelda's (with one exception).
Normal Attacks are the same, if her attacks have vertical knockback they launch in the opposite direction where sensible.
Neutral B: A Spell that absorbs projectiles instead of reflects them.
Side B: An Ice Spell instead of a Fire Spell.
Up B: Works like "Farore's Windfall" from Smash 4 (you can only teleport up, but if you hit when you reappear the hit spikes)
Down B: A Thunder spell, works like Pikachu's Thunder, but strikes either side of Hilda instead.
Final Smash: Basically the same as Zelda's. The Triforce piece spins in the opposite direction as a cosmetic difference.
If differences don't exist, you
make them.
Vaati as a Zelda Semi-Clone.
As a Toon Character, he has the same basic model as Toon Link (maybe slightly taller).
Normal Attacks are pretty much the same, but have Wind or Darkness cosmetic appearances.
Neutral B: A Wind Vortex that works like "Nayru's Rejection" (basically, it functions like a bi-directional Super Cape).
Side B: A Wind Spell which is basically Link's old Gale Boomerang.
Up B: Revali's Gale (...what?) | Okay, fine - "Farore's Squall" from Smash 4 (travels slower and deals no damage, but travels a greater distance and you push opponents away when you disappear)
Down B: Shadow Barrier (works like Mega Man's Down B, takes the form of Black Energy Spheres)
Final Smash: Vaati's Wrath (works like Mr Game & Watch's new Octopus Final Smash)
Wasn't
terribly hard, really.