A character's class in D&D represents a basic outline of their background, skills, and adventuring profession. Players have been adding new classes since the early days of gaming. There are multiple classes that have been printed in Dragon and other magazines. When we originally developed Toldara for 3E there were several classes we wanted to add to the standard list.
Assassin: I know there was a magic-using prestige class in 3E but I wanted a standard class like AD&D. I never got around to getting this one done. I did download a few Assassins from other players and some were very cool.
Battle Mage: A combination of fighter and wizard that could enchant his own weapons and those of his allies.
Elementalist: A character that harnesses the powers of the elements.
Priest: The Cleric represents the armor clad divine caster so why not have a robe wearing divine caster that performs miracles, cast spells, and can bless or curse people?
Witch: There has been a ton of Witch classes over the years. We wanted something that represented the fantasy vision of a witch. Someone that could put hexes on their enemies and had a familiar; only a limited list like cat, bat, and rat. Play up the fantasy stereotype.
I believe only two of these were every fully detailed by one of us. The other three saw various stages of detail but were never completed. We continued to work on them with D&D 3.5E but mostly abandoned them when we got the Pathfinder Core Rulebook and the Advanced Players Guide. My initial thoughts on converting any missing classes to B/X are detailed below.
Assassin: Look to the Blackmoor Supplement for inspiration.
Barbarian: Base it off the fighter but give them the ability to rage and more XP required to advance.
Bard: Not sure if I want to include this or not. I think it may be worth looking into.
Monk or Mystic: It has been around since the early days. I am thinking that it might better fit as a more western style monk.
Priest: Not sure what to do with this one.
Witch: I think it will be much easier to do for B/X. I am thinking of a spell caster with a familiar that is a bat, cat, or rat. Each familiar would map to one of the three alignments.
Demi Human Classes
Anshu: Feline humanoids.
Gnome: I have never really used them so I do not know what to do with them.
Half-Elf: I probably need to do up a half-elf class because several players have used them.
Half-Orc: Human and Orc hybrid with a social stigma and some of the Barbarian abilities.
Karnin: Canine humanoids.
Oranian: A winged bird-like race from the Oran Mountains.
Slarn: Lizard Men.
That should cover all of the bases and give plenty of extra and custom options for the world of Toldara. I am not even worried about a Psionic class or the chance of some sort of Psionic ability for characters so I am not even going to bother putting it on the list.