My priorities:
A cavalry class that doesn't harm a unit's speed growth, like a Scout or something, maybe sword-based like Beowulf from Fe4.
A masterclass with Swordfaire that doesn't harm a unit's speed growth, a Trueblade or something.
A class(-line) using lances that doesn't harm a unit's speed growth that's also accessible to male units, a lot of people mentioned halberdiers which I loved in Fe10.
A masterclass using magic that doesn't harm a unit's speed growth that's also accessible to male units.
My classes:
Scout, Intermediate Class
Skill Levels: Sword (C), Riding (D)
Growth Rates: HP (20%), Dex (10%), Spd (5%), Cha (5%)
Abilities: Canto
Swift Knight (I'd call them Vanguard but Ike Fans wouldn't approve), Advanced Class
Skill Levels: Sword (B), Riding (B)
Growth Rates: HP (30%), Dex (15%), Spd (5%), Cha (5%)
Abilities: Canto, Swordfaire, Terrain Resistance
Gold Knight, Master Class
Skill Levels: Sword (A), Riding (B+), Axes (C)
Growth Rates: HP (30%), Dex (20%), Spd (10%), Cha (5%)
Abilities: Canto, Swordfaire, Terrain Resistance
Ranger (basically a Master Assassin. Petra's post timeskip outfit would work perfectly for this one), Master Class
Skill Levels: Sword (A), Bow (A)
Growth Rates: HP (20%), Dex (20%), Spd (20%)
Abilities: Swordfaire, Sword Crit. +10, Woodland Stalker (negates movement penalty from forests and halves that of thickets)
Halberdier, Intermediate Class
Skill Levels: Lance (C)
Growth Rates: HP (20%), Dex (5%), Spd (5%), Def (5%), Cha (5%)
Skills: ---
Warden, Advanced Class
Skill Levels: Lance (A)
Growth Rates: HP (20%), Dex (15%), Spd (10%), Def (5%), Cha (5%)
Abilities: Lancefaire, Lance Crit. +10
Sentinel, Master Class
Skill Levels: Lance (A), Authority (B+)
Growth Rates: HP (20%), Dex (15%), Spd (10%), Def (10%), Cha (10%)
Abilities: Lancefaire, Lance Crit. +10, Ressourceful Commander (grants Gambit Uses x2)
Sorry for the text wall, I could think of plenty more classes if I wanted.