A bug in the system
So I did the Archmage since that makes a pretty iconic antagonist. Unfortunately, I ran into a stumper that I think I've been able to fix.
[sblock=Archmage Prestige Feats]
Archmage Training [Prestige]
You have begun training as an archmage.
Prerequisite: No other prestige feats, Skill Focus (Spellcraft), Skill Focus (Knowledge (arcana), Spell Focus in at least two schools of magic, any two metamagic or item creation feats, Spellcraft 11 ranks, Knowledge (arcana) 11 ranks, ability to cast 3rd-level arcane spells, character level 6th.
Benefit: The following skills become class skills for you: Concentration, Craft (alchemy), Knowledge (all skills taken individually), Profession, Search, and Spellcraft.
In addition, you gain a +1 to your caster level for every 2 prestige feats you posses.
Special: You may not gain this feat if you already possess any other prestige feats.
Arcane Fire [Prestige]
You can channel arcane spell energy into bolts of raw magical power.
Prerequisite: Archmage Training, Spell Focus (evocation), character level 6th.
Benefit: By expending a spell slot of any level you may channel a bolt of pure destructive energy. This bolt is a ranged touch attack with long range (400 feet + 40 feet/caster level) that deals 1d6 points of damage per caster level plus 1d6 points of damage per level of the spell used to create the effect. For instance, a wizard with a caster level of 6 who channels a 3rd-level spell into arcane fire deals 9d6 points of damage to the target if it hits.
Special: Learning this feat reduces your caster level by 2.
Arcane Reach [Prestige]
You can cast touch spells at range.
Prerequisite: Archmage Training, character level 6th.
Benefit: You may use spells with a range of touch on targets up to 30 feet away. You must make a ranged touch attack.
Special: Learning this feat reduces your caster level by 1.
Improved Arcane Reach [Prestige]
You can cast touch spells at greater range.
Prerequisite: Archmage Training, Arcane Reach, character level 6th.
Benefit: You may use spells with a range of touch on targets up to 60 feet away. You must make a ranged touch attack.
Special: Learning this feat reduces your caster level by 1.
Mastery of Counterspelling [Prestige]
Spells you counter are reflected upon their caster.
Prerequisite: Archmage Training, Spell Focus (abjuration), character level 6th.
Benefit: When you counterspell a spell, it is turned back upon the caster as if it were fully affected by a spell turning spell. If the spell cannot be affected by spell turning, then it is merely counterspelled.
Special: Learning this feat reduces your caster level by 1.
Mastery of Elements [Prestige]
You may alter the elemental components of spells you cast.
Prerequisite: Archmage Training, Spell Focus (transmutation), character level 6th.
Benefit: You may alter an arcane spell when cast so that it utilizes a different element from the one it normally uses.
This feat can only alter a spell with the acid, cold, fire, electricity, or sonic descriptor. The spell’s casting time is unaffected. The caster decides whether to alter the spell’s energy type and chooses the new energy type when he begins casting.
Special: Learning this feat reduces your caster level by 2.
Mastery of Shaping [Prestige]
You may alter the dimensions of spells you cast.
Prerequisite: Archmage Training, Spell Focus (transmutation), character level 6th.
Benefit: With this feat you can alter area and effect spells that use one of the following shapes: burst, cone, cylinder, emanation, or spread. The alteration consists of creating spaces within the spell’s area of effect that are not subject to the spell. The minimum dimension for these spaces is a 5-foot cube. Furthermore, any shapeable spells have a minimum dimension of 5 feet instead of 10 feet.
Special: Learning this feat reduces your caster level by 1.
Spell-Like Ability [Prestige]
Choose a spell you can cast. You gain that spell as a spell-like ability.
Prerequisite: Archmage Training, character level 6th.
Benefit: When gaining this feat, pick any spell you know. You permanently lose one spell slot of that spell’s level but can cast it as a spell like ability twice per day. You do not use any components when casting the spell, although a spell that costs XP to cast still does so and a spell with a costly material component instead costs you 10 times that amount in XP.
Special: This feat can be taken multiple times. Its effects do not stack, each time it applies to a different spell. Learning this feat does not reduce your caster level.
Improved Spell-Like Ability [Prestige]
Choose a spell-like ability you posses. You gain additional uses of that ability.
Prerequisite: Archmage Training, Spell-Like Ability, character level 6th.
Benefit: You can use your chose spell-like ability two additional times per day.
Special: This feat can be taken multiple times. Its effects stack. Learning this feat reduces your caster level by 1.
[/sblock]
The Archmage's standard rules for checks and balances (losing spell slots) doesn't hold up well in E6 because of how finite spell slots are. I used caster levels as the balancing factor here instead since it's easily tracked and manipulated. The problem that I ran into was this: you could theoretically take archmage prestige feats forever since there's not a limit like class progression. One could just just put in a tag under each feat chain on the maximum number you can gain, but I decided to ere on the side of overall consistancy: limit prestige feats to one prestige feat per HD. So now we have a max 6 archmage prestige feats. That grants a +3 to caster level. The character is probably going to have a 4-6 caster level penalty in his feat selection which can then be offset by the Practiced Spellcaster feat (or as you guys call it "Caster Training"). You'll still wind up with a character with significant power, though the initial feat would require a character of at least level 6+4 (so we're talking 6+6 at least before you're seeing this power). Considering the lofty prereqs for the class to begin with, this feels acceptable to me.
Considering adding a few of the Red Wizard of Thay's abilities to the archmage list, though that would be for my own use since it's non-cannon.
Other classes are comming along slower than anticipated due to my unwillingness to just turn class features into feats.