White Knight: A Knight with abilities similar to magic to atack or buff the team. Also strong against mages (idea came from templars and seeker from dragon age of all thing)
Black Knight: (yes,now it's a class) Similar to WK,but the oposite,debuffs enemies and abilities like dark magic
Battle Mage: I know some classes can use swords and magics but this one is a mage who equips heavy armor ,swords and tomes (def and res will need to be balanced)
Blood Mage: (some of you will get the reference): mages who use their own blood (HP decreases) to power up their spells.
Gunner: yes,I'm proposing guns be introduced to FE universe as a new ranged weapon,but maybe they can be a more medieval type of thing.
Gunners can reclass in to three paths instead of two: snipers (can atack with more range but not CC), bruiser (does more damage at close range with shotgun type and is more tanky) and soldier (balanced with a assault rifle ). A new element to balance them is ammo. You have a certain amount of ammo for each mission (can be improved with skills) and once you are out you're stuck with a combat knife (the bruiser class does more damage with the knife)
Witcher Bounty Hunter: Unit that does more damage to monsters and animals (including mounted enemies,pegasi,etc) can use swords and tomes (but tomes only to c rank). They have a weakness for sorceress tho
Machine: a new type of unit similar to the constructs in fates. they cant support or gain bonuses (if the game has dual support system) but they don't count as units so they don't take a space in number of deploy. They still have growths but instead of skills they gain improments (like more range,atacks that does more damage to mages,or armored units,etc)
They also have three promotions instead of two (but can only reclass between those 3): walls: the machine gets more defense but cant move (but get a powerfull counter atack),and archers gets bonuses when near them (like if they were shooting from the walls), breachers : focused on atack but a little fragile,can also blow up doors if you dont have a thief in hand,gets a boost to movement and speed and the last one is vehicle: the machine turns into a kind of a bus,it gains a huge boost to mobility (like move 10-11) and can carry two units but cant atack anymore (it has a weak counter atack). Also units get bonusses when inside them but can only counter atack ,good for moving your generals around.
Enginner: the enginner is a new class complementing the newly introduced machines. since the machines can't recover HP the enginners can repair them . they give bonuses to each other but the enginner is locked to his repair tool to atack . To not make they feel so useless or too situational,they can also repair your weapons (tho only once per battle and not legendary weapons)
Wizard: male version of the witches,instead of teleporting themselves they can teleport a ally (count as a action tho,like dancing)