One idea I have is having Edelgard's personal skill take part of her moveset as it gives her a Res boost when waiting after the timeskip, the way I see this translating for Smash is that she hits down B, has to wait a few seconds, and then gets granted temporary super armour. Whether it's limited to 1 attack or an arbitrary percentage, I don't know, but considering how axes are typically rather slow, temporary super armour could easily help out, especially with her Aymr combat art being easily translated as a move that could increase her speed when she lands a hit, or lets her cancel the animation to follow up with whatever she wants, or simply just have a lot of hitstun. I also think Assault Troop could be a cool special she's have, working similar to Zelda's Phantom and Ridley's Plasma Breath, if she gets to fully charge the move, a battalion of like 5 soldiers will appear and charge forward, staggering enemies similarly to how characters react when getting hit by all 5 Plasma Breath orbs. I feel it fits Edelgard's inherent knack at strategy as you can use the Assault Troop to force them to jump over the soldiers or get a mixup if they get hit by the troop