Just an idea for a homebrew feat...
Spellslinger
[General]
You're dedication to combat spellcasting has taught you how to cast spells as a part of a full attack
Prerequisite: INT 13, BaB 6+, Combat Casting, Ability to cast 2nd level spells
Benefit: When you use the full attack action, you can take a -5 penalty on your attack roll to cast any standard action spell in place of an iterative attack. You may replace up to 3 attacks in this manner, as long as you make at least 1 normal attack this round. The changes to attack rolls and Armor Class last until your next action.
Two-handed Spellslinger
[General]
You're dedication to combat spellcasting has taught you how to cast spells as a part of a full attack
Prerequisite: Two-weapon Fighting, Spellslinger
Benefit: You may forgo your offhand attack(s) to instead cast a single standard action spell. All normal penalties for using Two-weapon Fighting apply.
EDIT: Clarification on maximun number of spells