More types of weapon users would be nice. I'm not huge fans of either character but I like the idea of Bandana Dee because he uses a spear and would be more on board with Impa if she used her naginata instead of the Totally Not a Buster Sword 5000™.
Naginata indeed fits Impa better than the Biggorn Sword, but I think both would make for an awesome character. I had a composite Impa as an idea for a while, her being based on both Skyward Sword and Hyrule Warriors, and her summoning both the naginata and Biggorron Sword in her moveset, but them being elemental weapons. Much like how Greninja does it currently. It was also an idea Chrom supporters used to have, with Chrom being a character switching between his main weapons, Swords and Lances.
I could see Impa as an ideal stance character. Picture her with a stance that has the magical properties of Zelda, and the offensive agility of Sheik, and give her a middle of the road- stance that's more defensive than both. That would repersent Impa the Sage (Zelda-based style), her being a Sheikah (Sheik-based style) and her being Zelda's bodyguard / caretaker (guardian / monk-like stance).
With defensive stance / guardian / monk-like styles, I envision a character who fights with mostly palms and handchops, kinda like Wang, from Tekken.
Her having such a fighting style would empower her character, as it's a style of fighting that could fit the classic archetype of "Sage" especially with magical attacks involved in there somewhere. Her having a dual role in Skyward Sword as an old woman also is fitting with this, and her being a time traveller could even perhaps lead to time-related attacks? Like, slowing down time with a Special move for example.
There's also the Deku Nut, which used to be an item in Brawl but was removed for some reason. I could see that item make for a nice attack for Impa to.
I believe she still has solid chances. She and Dixie Kong seem the most likely pre-ballot characters to me.