If I'm asked to break the game down to four classes, these are two of them: the Spellcrafter, who learned to use magic, and the Gifted, who was given the ability to use magic. The rest is just differences in style. (ie a cleric is just a Spellcrafter who learned at a seminary.)
This works best if you assume magic is magic, and everyone's doing fundamentally the same thing with differences in the details (ie a wizard and a cleric casting detect magic are casting the same spell, using the same components, with only variance in subtle details and overall skill.)
For my own hypothetical heartbreaker, I'd make the different traditions wildly different, and overlapping spells are just re-using mechanics for convenience's sake rather than doing the same thing per se.
In Troika!, there are no "classes", only backgrounds. They all use the same rules for spells, but the background provides the "story" behind their skills and spells. I'll post two to illustrate.
53 Sorcerer of the College of Friends
As an integral part of your tutelage
in the sub-dimensional academy of
the Cordial Wizard God you spent
your childhood learning about the
fate of pixies, the colour of magic,
ritual grammar, and endless other
theoretical topics. Now you’re out
in the world, discovering that your
education hardly accounted for any of
the things that you’ve seen.
Possessions
• Pointed Wizard Hat you received at
graduation.
• Pocket Full of Wizard Biscuits (2d6,
each counts as a Provision).
• Wand used to help focus new
apprentices, now kept for
sentimental reasons.
Advanced Skills
4 Secret Signs – Witching Words
2 Run
1 Climb
1 Sleight of Hand
1 Swim
1 Sneak
1 Second Sight
1 Spell – Jolt
1 Spell – Amity
1 Spell – Mirror Selves
1 Spell – Protection from Rain
1 Spell – Helping Hands
1 Spell – Purple Lens
1 Spell – Random
12 Befouler of Ponds
You’re a wise man, a high priest, a
pond-pisser, a typical but committed
adherent of P!P!Ssshrp. The bloated
Toad God has no church other than
the periphery of ponds where the
foulness catches in the reeds and no
congregation other than the gnats
and dragonflies. You minister to them
all the same.
Possessions
• Sackcloth Robes, caked in stinking
mud and undergrowth. +1 to Sneak
rolls in marshy terrain while
wearing them, -1 everywhere else
‘cos it stinks!
• A Large, Worn Wooden Ladle
(Damage as Mace).
Advanced Skills
3 Spell –Drown
3 Swim
2 Spell – Tongue Twister
2 Spell –Undo
1 Spell – Web
1 Sneak
1 Second Sight
Special
You never contract disease as a result
of drinking stagnant liquids