Alm and Celica, huh? Sadly I don't think they're too likely based on the fact that FE16 is already in development, making them a case of missing the boat. Then again, Sakurai seems to like Gaiden, considering it has a few songs in Smash.
That being said, they're some of my most wanted characters. The full movesets aren't done yet, but here are the specials and general gameplay ideas I had for them!
Alm
Neutral: Anti-Fliers - Alm pulls out a bow and takes aim. However, it is pointed slightly upwards. Unlike Link's or Pit's, Alm's bow fires in an arc, making hitting with it harder. However, if it hits an aerial opponent, they will be sent straight downward. How far downward is determined by how long the button was held. This move has notable end lag afterward as Alm needs to reequip Falchion, but is a high risk, high reward move.
Side: Double Lion - A two strike move. The first, if it hits with its small hit box, has Alm quickly swipe the opponent, momentarily stunning them if it connects. Alm can follow this up by hitting side special again, causing him to slam down the Falchion from overhead for massive damage, but also hefty recoil. A move that could either help Alm flee to safety while the foe is stunned, or hit harder at the risk of the stun wearing off and Alm receiving recoil.
Up: Windsweep - Alm leaps straight up with the Falchion thrusted skyward. Does little damage, but Alm has super armor on the way up, referencing the Windsweep ability which prevents enemy counters.
Down: Subdue - Performed in a similar way to a Counter move, Alm strikes the opponent, but notably does no knockback, only damage.
Final Smash: Scendscale - If foes are in range of the attack's start up, a cutscene plays, based on Alm's in-game cutscene when activating this move. Visually, they're essentially the same. The move then ends. Unlike in Shadows of Valentia, this move does not cause recoil damage to Alm.
Alm's general gameplay revolves around having lots of moves that deal large sums of damage, but not a lot of knockback. Alm has no trouble racking up percentages, but actually killing is a bit of an issue for him, as besides his smashes his only kill moves are Double Lion's second hit, which had massive recoil and requires precision to use, and Anti-Fliers, which is also difficult to hit with. He's pretty damn fast though.
Celica
Neutral: Fire (Ragnarok) - Celica charges up a fire ball that shoots forward before exploding. At full charge, this becomes Ragnarok, which is incredibly powerful, doing roughly 35% damage and quite a bit of knock back, but at the expense of Celica taking hefty recoil damage. Chargeable and storable, but Celica continues to take more damage the longer it is stored, so releasing it sooner is recommended.
Side: Seraphim - Celica clasps her hands together as she is bathed in a flash white light. A giant ball of white light descends from the sky once the side special is input again, or until ten seconds have passed, causing it to fall automatically. A trap-styled spell to catch goes off guard once they forget where it was summoned from. Celica is only damaged with this move if the move hits the opponent, unlike Ragnarok.
Up: Excalibur - Celica summons a gust of razor wind around her as she ascends. Nearby foes get cut by the wind, though Celica also takes minor damage from this move (less than five percent).
Down: Mila's Turnwheel - Celica kneels and enters a praying stance. If this move is held for five seconds without breaking, Celica's damage percentage will reset to how it was thirty seconds prior to use. Celica must be on the ground in order to use it.
Final Smash: Ragnarok Ω - If foes are in range of the attack's start up, a cutscene plays, based on Celica's in-game cutscene when activating this move. Visually, they're essentially the same. The move then ends. Unlike in Shadows of Valentia, this move does not cause recoil damage to Celica.
Celica mainly relies on her spells, with a few moves utilizing the Beloved Zofia, like her jab. She takes a variant of Pichu's self damage gimmick, but better executed. Celica does more self damage the more potent her spells are, but can reliably kill using them. Her issue stems from her being the epitome of a glass cannon, as she can't take hits well at all, especially when using her higher recoils spells.
If you want visuals for their Final Smashes, have a look here at this short clip. Bonus Triangle Attack too.