... With a set of, say, 4-6 total subclasses for each class, ...
... So: 13 classes ...
Rough math tells me that's between 52 and 78 possible class-subclass combinations, each one needing its own rules and write-up and each one then needing to be vaguely balanced against each other both before and after the corollary variable of PC species is introduced.
Have fun with that.
I'd start - and stop - with 15-20 hard-coded and easily-identifyable classes. No subclasses. Each of those classes has clear strengths in some things and obvious weaknesses in others, with limited bleed-over and hard niche protection. Bang - there's the archetypes.
The thing we'd have to accept is that there's a few archetypes that just don't play well with a game built around party interdependence, the most obvious (and, sadly, most popular) of which are the "I can do everything" archetype and the "I'm the boss" archetype. So, those get punted.
My class list might look something like:
Warriors:
--- Knight (shiny armour, etc.)
--- Swashbuckler (light-armoured, ranged or melee)
--- Veteran (basic mercenary type)
--- Ranger (woods warriors, non-casters, no animal companion)
Rogues:
--- Thief (basic sneaky-scouty type)
--- Assassin (hired killer or spy)
--- Charmer (talky persuasive type)
--- Dancer (genericized wire-fu type, replaces Monk)
Casters:
--- Cleric (divine caster as usual)
--- Nature Cleric (a.k.a. Druid, covers Shaman as well)
--- War Cleric (covers Paladin also)
--- Diviner (divnination spells etc. mostly go here)
--- Illusionist (mind-screwers, charmers)
--- Necromancer (they make things dead then play with the corpses)
--- Summoner (summoning, gating, conjuring spells and familiars/animal companions exclusively go here)
--- Mage (artillerists and buffers)
Oddballs:
--- Psionicist (if it can be made to fit without hosing Illusionists' screw-with-your-mind niche, debatable)
--- Tactician (maybe best as a non-adventuring class?)
--- Artificer (or Tinkerer; specifically for games/settings that have lots of devices and tech)
What's intentionally missing?
--- Swordmage - the classic "I wanna do it all" class - gone in any form.
--- Bard - can't make it fit between Charmer and Illusionist - gone.
--- Warlord or Leader - classic "I'm the boss" class, also healing is strictly Clerical.
--- Barbarian - can't make it fit between the other Warrior classes except as a very boring one-trick pony - gone.
--- Multi-classing - gone.