Some weaks ago I had a similar idea, but I forgot to post it:Speaks said:Practiced Spell Caster - general - benifits those you are not casting spell at their full hit dice. bascially you get a +4 level to determine the effect of a spell but you do not get more spells as level increase. Also can't go above your hitdice for spell levels. So a fitr3/Cleric5 with this feat can cast his cleric spells at 8th lvl effects .. if he levels to ftr4/clr5 he cast at 9th level effects. Basically no extra spells but cast yous at greater effect .. much like a bead of karma. Need four ranks of spellcraft for the feat.
Improved Spellcasting [General]
Prerequisite: Multiclassing with at least one spellcasting class.
Benefit: Choose one spellcasting class. You gain new spells per day (and spells known, if applicable) as if you had also gained a level in this spellcasting class you belonged to before you took this feat. You do not, however, gain any other benefit a character of that class would have gained. This essentially means that you add +1 to the level of some spellcasting class you have, then determine spells per day, spells known, and caster level accordingly.
Special: A character may gain this feat multiple times. Choose the spellcasting class. Its effects stack for the same spellcasting class. If you would gain a caster level greater than your character level, then the effect of this feat is suspended until you gain a level in another class which doesn't improve your caster level.
With this feat you can take non-spellcasting classes without losing power - as long the mixture is two-thirds spellcasting. A Fighter 6/Wizard 14 has then a caster level of 20, but otherwise with the general feat at first level only 4 fighter and 2 metamagic bonus feats available, has 6d10 + 14d4 + 20xCon-modifier of hit points available (ignoring the full hit die at first level). A Cleric 6/Wizard 14 has a Wizard caster level of 20 and is the same as above, except the exchange of Fighter abilities to Cleric abilities and hit dice. A Cleric 1/Wizard 19 has a Cleric caster level of 7, 3 metamagic bonus feats and has 1d8 + 19d4 + 20xCon-modifier of hit points available.
After Upper_Krust's CR system, a feat is worth +0.2, while primary spellcaster level are worth around +0.4 - the doubled value as a normal feat. WotC's solution may cost at least around that. So, are the above mentioned combinations too weak compared to Practiced Spellcaster?