Prestige Classes and Specialists

Why are specialist mages (Diviner, Evoker, Necromancer...) not
prestige classes? Wouldn't it make better sense to have
specialization as such? I.e., you hit Level 3 and you can optionally
specialize.

Something I've been thinking about is a *very* short Prestige Class,
the Magical Specialist.

Hit Die
D4

Requirements
To qualify to become a Magical Specialist, a character must fulfill
all the following criteria: Knowledge (Arcana) 5 ranks, Spell Focus,
Able to cast 2nd level arcane spells.

Class Skills
The class skills (and the key ability for each skill) are
Concentration (Con), Craft (Int), Decipher Script (Int), Knowledge
(all skills, taken individually) (Int), Profession (Wis), and
Spellcraft (Int).

Skill Points gained
2 + Int modifier.

Class Features

Weapon and Armour Proficiency
No proficiencies with weapons or armour are gained with this prestige
class.

BAB +0
Fort Save +0
Reflex Save +0
Will Save +2

Spells per Day
When this prestige class is taken, the character gains new spells per
day (and spells known, if applicable) as if he had also gained a level
in the arcane casting class that qualifies him for this prestige
class. He does not, however, gain any other benefit a character of
that class would have gained.

Specialist

When this prestige class is taken, the character becomes a specialist
in the school selected for his Spell Focus. In addition, the
character at this time must choose two schools (one, if he is focusing
on Divination) which are now opposed schools. As this prestige class
can be taken multiple times, the opposed schools cannot be ones which
have been previously chosen.

By taking this prestige class, the Specialist can memorize one extra
spell per level per day of his selected school. In addition, he gains
a +2 bonus to Spellcraft checks to learn spells of his selected
school, and a -4 penalty to learn spells of his chosen opposed
schools.

Spells of the selected school gain a further +2 modifier to their DC.

Spells of the opposed schools can still be memorized and cast, but in
order to cast them successfully, a DC (25 + spell level^2)
Concentration check must be made. They gain no penalty to their DC.




I thought about making this a Feat, but that would mean cutting into
the already limited number of Feats that a character can take.

Why are specialist mages (Diviner, Evoker, Necromancer...) not
prestige classes? Wouldn't it make better sense to have
specialization as such? I.e., you hit Level 3 and you can optionally
specialize.

Something I've been thinking about is a *very* short Prestige Class,
the Magical Specialist.

Hit Die
D4

Requirements
To qualify to become a Magical Specialist, a character must fulfill
all the following criteria: Knowledge (Arcana) 5 ranks, Spell Focus,
Able to cast 2nd level arcane spells.

Class Skills
The class skills (and the key ability for each skill) are
Concentration (Con), Craft (Int), Decipher Script (Int), Knowledge
(all skills, taken individually) (Int), Profession (Wis), and
Spellcraft (Int).

Skill Points gained
2 + Int modifier.

Class Features

Weapon and Armour Proficiency
No proficiencies with weapons or armour are gained with this prestige
class.

BAB +0
Fort Save +0
Reflex Save +0
Will Save +2

Spells per Day
When this prestige class is taken, the character gains new spells per
day (and spells known, if applicable) as if he had also gained a level
in the arcane casting class that qualifies him for this prestige
class. He does not, however, gain any other benefit a character of
that class would have gained.

Specialist

When this prestige class is taken, the character becomes a specialist
in the school selected for his Spell Focus. In addition, the
character at this time must choose two schools (one, if he is focusing
on Divination) which are now opposed schools. As this prestige class
can be taken multiple times, the opposed schools cannot be ones which
have been previously chosen.

By taking this prestige class, the Specialist can memorize one extra
spell per level per day of his selected school. In addition, he gains
a +2 bonus to Spellcraft checks to learn spells of his selected
school, and a -4 penalty to learn spells of his chosen opposed
schools.

Spells of the selected school gain a further +2 modifier to their DC.

Spells of the opposed schools can still be memorized and cast, but in
order to cast them successfully, a DC (25 + spell level^2)
Concentration check must be made. They gain no penalty to their DC.




I thought about making this a Feat, but that would mean cutting into
the already limited number of Feats that a character can take.