3.X Spellcaster thought experiment

[Logic]

Spells are broken. This is an almost universally accepted truth.

But how does the game change if all classes with spellcasting ability are suddenly prestige classes with entry requirements making them available at 4th character level?

Druid, cleric, and Wizard get a 9th level spell as a capstone, for one.
Magical healing prior to level 4 is non-existent (barring potions or wands likely out of the price reach of some parties.)

But does this proposal fundamentally change anything after level 3?

[Djinn_in_Tonic]

But does this proposal fundamentally change anything after level 3?

It reduces the number of high-powered spells available, and it does delay the rate at which those spells are gained. So you succeed somewhat.

Conversely, no access to healing makes the early levels significantly more painful.

Ultimately, however, even late spell acquisition doesn't help in the really high levels. It flattens out the rate at which spellcasters surpass mundane characters (I'd guess it would be around level 10-13 rather than 6-7 using this sort of system, depending on the rate these prestige classes grant spells), but it still doesn't change the fact that mundane characters scale linearly, and spellcasters scale quadratically. You've just pushed the intersection ofthe two lines up a few levels.