While I largely agree,
@Ruin Explorer and
@TwoSix, I think there are different class fantasies you can explore through different mechanics. And sometimes building mechanics and then looking for the fantasy that fits the best is a good thing.
I sincerely, and unpopularly, believe, though, that while Warlocks should exist as distinct from other spellcasters... Sorcerer and Wizard should just be folded into one class.
Wizard Spellbook, Sorcerer Metamagic, same class. The whole "Sorcerers are different because they won the genetic lottery!" angle should really just be a subclass of Bard that is just magically inspirational rather than musically so.
Why? Because when we see the classic "Born with inherent magic and a destiny" character in media they're almost invariably non-musical bards! They cast arcane magic but also have the ability to cast healing magics, they inspire others and provide buffs to the powerful warrior character who winds up protecting and/or falling in love with them...
Sorcerer, honestly, was a bad attempt at the "Chosen One" narrative being a whole class and was designed in 3e to be the "Easy Spellcaster" since you didn't have to fiddle with spellbooks and memorizing different spell lists. Which most Wizards don't even bother with! They tend to use a largely fixed Spell List for themselves and only occasionally swap out a spell based on the situation.
I can't think of any wizard I've seen since 3e that changed their spell list on the daily. Hell, I don't think I saw that in 2e other than grabbing 2-3 copies of the same spell rather than 1-2 copies on days they felt they'd need more
Fireball.
But the Psion/Esper? Definitely needs it's own class. Warlock, too.
I also like designing classes based on mechanical holes or challenges and back filling narrative, though, too. >.>

The Champion and the Warcaster in Martial Artistry are going to be like that. Warcaster was me breaking the "Can't use Combat Maneuvers with Spells" rule to make a Cantrip-Wielding ranged combat gish, while the Champion is all about marking targets to protect and attack.
The narratives that I wound up with were "Low-complexity magic wielded with finesse makes dealing with magical and monstrous threats resistant to BSP more reasonable, so military academies train gish" and "Dedicated to a cause beyond themselves to the point of embodying it to their dying breath".
Granted, you could probably take a Herald/Paladin subclass for the Champion and call each of the causes it's own oath, have those oaths provide marking abilities or whatever... but you wind up with two big problems:
1) It's still a divine/martial spellcasting hybrid rather than a martial class.
2) You don't have much room to build the concept in, since you only get 4 subclass levels (3rd, 7th, 15th, 20th)
I think the big thing, there, is striking a balance between the pigeonholing and the overly broad. Sorcerer/Wizard? Overly broad and overlapping so badly they should just be one class. Warlock? Strikes the balance. Illrigger? Pigeonholed to Hell and back.
Literally.