If there's any character that would be a perfect sense Echo Fighter and where the status would be beneficial to getting them in, it'd be Paula from Earthbound/Mother 2. Make her an Echo of Lucas, but she uses Ness' throws and PK-Fire and Magnet. Think about it, all of Ness' and Lucas' Special moves, aside from Flash, can be used by her, she can use a Frying Pan for her Forward Smash and while she can use a Yoyo, it'd make alot of sense for her to use Lucas' Up-Smash and Down-Smash as she is the main "Black Mage" of her game.
And she has a full model in Smash Ultimate, helping with PK Starstorm alongside Poo for Ness' Final Smash, just like Chrom with Robin's Final Smash. She'd also be on the much more unlikelier side of characters that could become playable for Smash.
Besides changing her throw to be like Ness', as she doesn't have a rope snake compared to Lucas, her Up-Smash and Down-Smash' special effects can be changed to a PK-Freeze/Fire effect and you could have her Up-Smash be alot more faster, but weaker in power compared to Lucas. Heck, by making the PK effect a PK-Freeze effect, you could potentially have her Up-Smash freeze foes. And for her specials, she can have PK Fire and PSI Magnet from Ness, while she gets PK Freeze and Thunder from Lucas. Making her a middle ground between Ness and Lucas.
Her Final Smash could've been her Pray command from Earthbound, but unfortunately the topic of Prayer has started becoming a controversial topic, especially in Europe, so most likely, she'll keep PK Starstorm as a Final Smash and have Ness and Poo help her.