In my boredom I have been fantasising about potential Impa movesets, and thought I would share. I think SkySwo Impa would be the one that makes it in - I think it's unlikely they'd use a model from a 2nd-party game that's non-canon. I'd also prefer Impa not ti have a sword tbh, there's already so many swords, and I actually prefer her look in SwySwo...I think it's more representative as her as a character.
Anyway, here's what I have theorized.
Neutral B - Shield of Light
Impa summons a quick shield as demonstrated here
Obviously on a much smaller scale, but maintains the blue colour and oval shape. It protects her from projectiles and can also push enemies away.
Down B - Sacred Orb
Impa creates a projectile as seen below:
She can then throw it as Link would a bomb. However, unlike a usual projectile, it remains airborne and does not drop. It slows down in speed, until it comes to a stop, where in then remains stationary in the air for a few seconds before disappearing. If a player runs into the floating orb, they are knocked back as if it were a bumper. This could make for an excellent spacing attack.
Side B - Sheikah Slide
Impa equips her dagger, and then charges at her foe in a sideways direction. This attack has minimal knockback but can deal good damage. Think of it similar to Fox's side B, she first equips the dagger and then charges very quickly. The dagger remains close to her chest (mainly because flailing a dagger at someone and charging is probably a bit to PG13).
Up B - Hylia Flume
Impa is guided by goddess Hylia who delicately lifts Impa upward at a 90 degree angle. The spirit appears behind her, and then guides her up. The 90 degree angle makes this attack complicated. On the one hand, if successfully performed, it can guide Impa completely over the ledge and right onto the stage again. However, if you're too far down, you'll end up being guided under the stage.
Final Smash - Gate of Time
Impa transforms into Old Impa from Skyward Sword. The Gate of Time appears behind the stage and opens. Then, the Imprisoned is released. He falls downward, causing great knockback on anyone that is hit. Think of this like Snorlax except much more powerful and bigger.
....
So those are just some ideas I had. I think her regular attacks could be swift kicks and arm jabs to represent her Sheikah nature. Maybe her grabs could get people by the ear (or side of the head) to represent her motherly/authoritative nature in the game.