Well, I will go on a record to say that I am in no way hoping for Tiki to appear and she was just a random Fire Emblem character I pulled out on the spot. But, even then, I will say I could more easily imagine a moveset for Tiki than I could, say, Jigglypuff or Captain Falcon.
I wouldn't be upset if she could use the dragonstone without actually transforming. She could spit out blasts of divine energy. She could take moves that are inspired by tomes, such as "Arcwind" being a move that will create a massive pillar of wind that sends her soaring upwards. Maybe transluscent dragon-claws manifest for her smash attacks that mimic her motions... the possibilities are endless. She can fly. She can be the original Tiki, small, agile, light, or the recent Tiki, with greater physical reach. She could even make use of the Fire Emblem and/or its gemstones, each manifesting a different attack.
I could make just about any character or class from Fire Emblem into a fun character that offers something unique to the roster. It is not a matter of whether or not a character can be done, so much as if it should be done when another Nintendo character would be more fitting.