NaturalZero
Hero
The first thing i would do is toss out the 3-18 ability scores and make the actual ability score number and the modifier number the same thing. There's no reason to have 18, 16, 13, etc, on the page when 4, 3, and 1 are the numbers you use. I know, this is a class thread and this isn't a class critique but it's the lowest hanging fruit when it comes to streamlining the game.
As for class structure, I'd actually like to see things modeled on the Legend d20 system. There, each class has 3 "tracks" of abilities. A barbarian might have a "rage" track and an "ancestral spirits" track and a "weapon master" track, for example. The way multiclassing works in this paradigm is that you choose to sacrifice one of your tracks of abilities in order to replace it with a track from a different class. A wizard might swap out a track that grants direct-damage spells in order to get a fighter's martial maneuvers, or a cleric might sacrifice the healing track in order to get the druid's shapeshifting track. Certain things, like tracks that increase damage (rage, sneak attack, hunter's quarry, et al), wouldn't stack with each other, nor would the ability to command multiple types of summons (so no zombie horde + golem legion + elemental servants at the same time on the same turn) encouraging players to make characters with a broader set of abilities. Feats are present to represent dipping and changes that occur as the character evolves during the campaign, since the system won't have people dipping classes levels left and right as they progress.
Subclassese here are just additional tracks that can be swapped into a build. Want a plant control build? That's a new track that replace one of your druid (or any class) tracks. Need more elemental flavor? An elementalist track can take the place of one of your 3 default choices. Racial tracks could also be a thing too. Swap one of your fighter tracks out for a progression of dwarf abilities or remove a wizard track and put your special elven bladesinger subclasses in it's place.
As for class structure, I'd actually like to see things modeled on the Legend d20 system. There, each class has 3 "tracks" of abilities. A barbarian might have a "rage" track and an "ancestral spirits" track and a "weapon master" track, for example. The way multiclassing works in this paradigm is that you choose to sacrifice one of your tracks of abilities in order to replace it with a track from a different class. A wizard might swap out a track that grants direct-damage spells in order to get a fighter's martial maneuvers, or a cleric might sacrifice the healing track in order to get the druid's shapeshifting track. Certain things, like tracks that increase damage (rage, sneak attack, hunter's quarry, et al), wouldn't stack with each other, nor would the ability to command multiple types of summons (so no zombie horde + golem legion + elemental servants at the same time on the same turn) encouraging players to make characters with a broader set of abilities. Feats are present to represent dipping and changes that occur as the character evolves during the campaign, since the system won't have people dipping classes levels left and right as they progress.
Subclassese here are just additional tracks that can be swapped into a build. Want a plant control build? That's a new track that replace one of your druid (or any class) tracks. Need more elemental flavor? An elementalist track can take the place of one of your 3 default choices. Racial tracks could also be a thing too. Swap one of your fighter tracks out for a progression of dwarf abilities or remove a wizard track and put your special elven bladesinger subclasses in it's place.