Custom Practiced Spellcaster Feat

I'm in a game where I'll be the primary Arcane Caster, as a Gish.

So I'm looking to throw together a feat that works in the way of Practiced Spellcaster, but for Spells Per Day.

I won't be stepping on the toes of a primary caster, so I'm looking to boost spellcasting to still be the primary caster.

If one were to make such a feat, how much of a boost would it give?

Should Practiced Caster be changed to include it, and then just provide a smaller boost instead of +4?

It's okay if it ends up a little shenanigansy, it's a rather unusual campaign. (All the players have domains as a cleric - divided up ALL the domains evenly).

So: Normal
Practiced Spellcaster
+4 to Caster level, up to your character level. Doesn't increase spells per day.

Practiced Spellcaster Revised
+2 Spellcasting in Existing Caster Class, up to Character Level. (Like PrCs that Grant Spellcasting)

That would be too strong. And imagine the potential for abuse -- avoiding loss of spells known levels (SKL) is the major issue when selecting PrCs for primary casters.

For reference, see Spellcasting Prodigy from PGtF -- this one increases your spellcasting attribute by 2. See PHB, p. 8 or the SRD: Normally, this increase grants you one more spell (of one level above the highest bonus spell you had before applying the feat). If your attribute is really high, it will grant additional spells of the lowest levels.

Then there is also the feat Extra Slot.

I suggest looking at those feats, either taking them or designing something on par with them.

Hmm. The point is access to higher spell levels. How would you do it with that in mind?

Would +1 level of existing spellcasting class be too much for a feat?(obviously would not let you go above character level.)

Yes, IMO it would be too much for a feat. Although there are feats that might be stronger than that in other categories (I'm thinking of Chain Spell, for example), if you look at the feats granting extra spell casting, it is too powerful (I think Spellcasting Prodigy is the benchmark, here) -- it includes the main reason to take a class level. Note that the Paragon Classes (and other PrCs) come with a lot of advantages, and are mainly offset by causing the loss of one SKL.

In Complete Arcane (p. 181), there is Precocious Apprentice, which grants you access to a single second level spell as a first level caster. When you get access to second level, you keep the spell as an additional second level spell slot.

I think you could design something like that, but I think it is a balance issue compared to Precocious Apprentice, because the 2nd level limit was design intent. I guess designers felt that access to a single second-level spell above your own SKL is pretty strong -- and that they felt that if this is possible for higher level spells, it would be unbalanced (like a feat granting access to one 9th level spell, when you are SKL 15). Really just guessing here, but that's my impression. So you'd need a drawback, probably, like using a spell of a lower level to power it -- something like using two spell slots of level 4 to power one spell of level 5 (I think there's a class ability or feat out there that does exactly this).

You could, also, design a feat chain, with the entry feat granting little advantage. Something like:

Initiated Mage:
+1 bonus on Spellcraft

Intense Mage:
Add +1 to your caster level (same as Practiced Spellcaster, does not stack with Practiced Spellcaster). Requires Initiated Mage.

High Mage:
Add +1 to your level for spells known, up to your HD. Does not affect caster level. Requires Intense Mage.

So effectively, you need two substandard feats to get one which is very powerful.

Even with this chain, I don't know if it would be balanced -- allowing it means that you can take a level in a different class (or take a PrC that's balanced because it costs you a SKL) at no penalty at all. Using it is a pretty big boost, and a wizard at level 16 would gain one 9th level spell and one 6th level spell.

I definitely think that dropping the first as a requirement would be too powerful, unless there are some additional drawbacks. The Practiced Spellcaster overlap would, IMO, not be enough, because there are some situations in which you only need to gain one caster level to offset PrC drawbacks.

Another strategy could be to limit the benefit to a chosen school, which might be complicated in practice, but a limiting factor.

I think sort of thing works well if and only if you don't also have access to PrC's in the campaign.

I have my own system, but it works more like this:

Practiced Spellcaster
+4 to Caster level, up to your character level. Doesn't increase spells per day.

Well Practiced Spellcaster
Prerequisite: Practiced Spellcaster, character level 6
Increase your effective Caster level by two for the purposes of spells known and spells per day up to your character level.

Interdisciplinary Student
Prerequisite: Practiced Spellcaster, Well Practiced Spellcaster, character level 12
Increase your effective Caster level by an additional two for the purposes of spells known and spells per day up to your character level

This has come up before in the house rules forums. The effects at high level are comparable to Gish type PrC's without the need for alot of PrC's, in as much as PrC's that faciillitate multi-classing as a spellcaster usually involve trading a few feats away to gain bonuses to your caster progression as well. The worst case in terms of abuse of power level are roughly comparable to the worst case abuse with the PrCs, and in my opinion there isn't that strong of a reason to go this route over single class provided a bit of other balancing is introduced (in particular, you need the sort of 'end reward' design Pathfinder implements).