• sorcerer (charismatic, instinctive, emotional, magic as nature and not a choice)
• warlock (sneaky, roguey, cunning, magic as unnatural)
• wizard (smart, scholarly, magic as an active ongoing choice)
are just too different to coexist in the same class.
Whether someone is "emotional", "roguish", or "scholarly", is in the biography part of the character sheet, that describes personality, including Bond, Quirk, Flaw, Ideal, and Alignment.
It is a narrative that is separate from the class, and strictly separate from mechanics. Obviously, some Wizards are emotional, and some Sorcerers are rational. Some Warlocks are sneaky, and other Warlocks are reluctant, or defiant. It all depends on the players own character concept.
It is somewhat unhelpful to design a class around a "mood", especially when players have diverse moods and perspectives.
I am confident a single class can accommodate all three, Sorcerer, Warlock, and Wizard.
For example, a Psion with a Warlock mechanical chassis, Short Rest spell points, and a player choice of any mental ability for the casting ability, can easily have subclasses for each one of these concepts: gift, pact, and scholarship.
For design, it is far more important to focus one what mage character DOES.
A Wizard reads a book. So what? How does this literacy affect what a Wizard DOES? In this case, the research and records amasses an understanding of many different kinds of spells. So, mechanically, the Wizard can easily swap one "prepared" spell for a different one. The other mage concepts dont have this versatility. The other mages are more specialized, focused, and dedicated to a theme.
A Psion who can easily swap spells, feels like a Wizard, even if there are no books.
A Sorcerer trains to develop ones personal magical talent, similar to an athlete training. Albeit, this talent might be an inhuman one inherited from ancestor of an other species. The sorcery requires tremendous self awareness and discipline − even while some express this discipline as that of an obsessive artist or virtuoso musician. The Sorcerer specializes in a magic thematically, and does it well, and comes to do it easily as a habit. The mechanics of metamagic intends to express this concept of a virtuoso. There is less access to spells but the spells are more effective.
More design work is necessary to actualize the concept of "innate" magic. For example, spells that require a Material Component are horrifically non-innate. The components line needs to delete from every spell description. Each class and subclass defines its own method for spellcasting.
Both Wizard and Sorcerer are innately magical. But they approach magic differently, according to different to different methods and techniques. The Wizard explores the magical properties of ordinary objects, such as plants and stones (the Material Components), to discover and apply the principles of magic inherent in the multiverse − the Weave. The Sorcerer relies on ones own personal magical to selfexpressly influence the world around one. Often there are aspects of the multiverse that the Sorcerer intimately resonnates, such as Dragons, or Elemental energy, or Celestial being. In some ways, one incarnates these beings, heightening a thematic specialty.
The Sorcerer is the same thing as a Warlock. Whether a pact transforms the mage or an inheritance transforms the mage, the mage is gifted magically, a protegy without the need to "study" and whence a tendency to focus magic thematically. The mechanics of each augment a spell, whether by metamagic enhances it or by an invocation enhances it. The Warlock tends to have more always-on powers, more potent than cantrips − but one would think a Sorcerer with bodily magic, instincts, and reflexes should too, like an athlete jumping whenever.
A Warlock makes a "pact" with a powerful being, or sometimes inherits the magic from an ancestor who made a pact. Reciprocally, A Sorcerer can make a pact, in the sense of being personally transformed by a powerful Dragon, Fey, or Celestial. The Warlock and the Sorcerer are the same.
A Psion base can easily handle subclasses for Wizard, Sorcerer, and Warlock. It looks like only two subclasses are necessary.
An example of what would differ is, a Summoner. (Elric comes to mind, for those familiar with the books about him.) The Summoner makes "pacts" with various beings, including powerful ones, and summons them to perform tasks, often by means of rituals and contracts. The Summoner never casts the
Fly spell. Instead, the Summoner conjures an Air Elemental to carry oneself. The Summoner never casts
Cure Wounds. Instead, the Summoner conjures a Unicorn who heals. And so on. The Summoner is DOING magic differently.