Cavalier wouldn't be doable with the design of the game.
Disagree ...
Right now im playing in campaign, where one of us play Cavalier Fighter / Ancestral Barbarian ... and while we have no mounts (i asume that was your point?) Cavalier is still quite usefull addition to party.
So it would be doable ...
Probably it wouldnt be 1:1 with tabletop ... but since Swasbuckler, and Bladesinger are not either ... i would dare to assume Larian wouldnt really mind that.
Also ... Cavalier is basicaly best Fighter Tank ...
And this game dont have any dedicated Tanking spec ... so that would bring something "new".
Samurai wouldn't really fit thematically.
Disagree again ...
As far as i know, there is nothing odd about Samurais in DnD ...
Yes, i know we have that word tied in our little minds with feudal Japan ... but that is just same word for something entirely different. :-/
Rune Knight kind of competes with Giant Barbarian.
How?
Ok, they both go big ... and?
Rune Knight is quite versatile subclass, while Giant Barbarian is weapon throwing elemental brute ... there is not much simmilarity.
And if you really mean this as arguing point, then im affraid i have to insist that in that case Arcane Archer competes with Range Ranger ...
After all one old DnD joke says:
"What is best way to play a Ranger? Play Dex based Fighter instead."
Psi Warrior is basically Battlemaster 2.0
Battlemaster is a dude who is really good with his weapon ...
Psi Warrior is a jedi. xD
Also ... even if ... disclaimer: i dont agree with it, but lets say for argument purposes ... isnt Psi Warrior quite litterally and by deffinition the MOST FITTING SUBCLASS FOR GITHYANKI?
Banneret is kind of boring.
Yup.
No arguments there, they sucks. xD
Echo probably being hardest to implement
Maybe ...
Still, it would be cool.
