Idon
whats the source of that image in your signature?
BTW regarding making Lyn unique... i don't think it would be particulary hard even if you don't touch the bow. personally i think that would be an interesting concept if her sword is always sheathed for her tilts and smashes to be compromised by either non sword moves or very fast and powerful, but very commited slashes.
For example jab would be a quick pummel hit that doesn't kill or do much damage, but have decent kockback to work as a spacing tool, down tilt a very quick kick that don't do much damage, but is good to test your oponnent reactions, forward tilt a decent but not great kick with not much endlag, but if you input again it becomes a 2 hit moves were she unsheathes her sword and do a quick slash, for good damage and set knockback, but punishable endlag.
up tilt similar to forward tilt but starts with a upwards pummel.
Then smashes would be her unsheating her sword with lots of power and little start up (fast) but tons of endlag meaning any whiff would be punished heavily. (say she needs to re sheat her sword).
This would be interesting in the sense Iaijutsu sense that while deadly, every time she unsheathes her sword should be calculated and commited and would mimc the Iaijitsu philosophy of getting rid of all usless motions in order to reach speed.
And certainly would be inmmmediatly different to marth/ ike and teh swordsman archetype that is "look at me throwing all this safe attacks that you cant punish anywyas due to me spacing" kinda pressure.
Other interresting idea (albeit completely different) is that her attacks not only include a hitbox, but also a movement , meaning that you should be minding not only your hitbox but also where you are moving your hurtboxes in order to keep them safe. which would go to the "Agile swordfighter" archetype, while still having attacks with high commitment but you need to manage your spacing different in order to make them safe.
Finally since there is the classical samurai archetype having multiple swords and this being Fire emblem, a mechanich where she can switch blades could also work very well, her attacks animation and hitboxes would be teh same, but different swords would give different attributes. (Shield breaker extra shield damage at teh cost of knockback, Killing edge can reuse the item mechanichs that deals extra damage and knockback during certain intervals, Silver sword would be the standard, etc) considering she would be fighting with her sword sheathed most of the time, wouldn't look awkard for her to switch swords as a special move. If you played Muramasa, they can also add a quick graphic to signal the sword change.
As for aerialas, an idea could be that her aerials doesn't have the arcs that are so good for zoning, but makes her change her air direcction, in order to make her more evasive (think stuff like mii gunner forward air or a down air that stalls her fall) Also not having those sweet archs other sword fighters havewould mean that her attacks should be more precision based.
Add some standar "movement specials" like a version of metaknight's "dimensional cape" as up b, something akin to "fox illusion" as side b... and you get yourself a pretty unique fighter that uses a sword. and fits the myrmidon archetype. as for the AT, just replace her with the next more popular myrmidon and you are done.