How about a new feat?
Two-Weapon Parry
Prerequisites: BAB +6, Combat Expertise, Two-Weapon Defense, Two-Weapon Fighting
Benefit: When fighting with two weapons, you may select one of your weapons as an offensive weapon and the other as a defensive weapon. In effect, you may apply your Combat Expertise dodge bonus to armor class from one of the two weapons and not have the associated attack penalty apply to the other weapon. Your offensive weapon's attacks drop by -2.
Note: With Two-Weapon Defense, your off-hand weapon grants you a shield bonus to your defense. When using Two-Weapon Parry, you gain a dodge bonus (see Combat Expertise), you do not gain the shield bonus (from Two-Weapon Defense). You may, of course, choose to use Two-Weapon Defense instead of Two-Weapon Parry on any given round.
Example: Drest wields two kukris with attack bonuses of +12/+7/+2 and +12/+7 (he has Improved Two-Weapon Fighting). He's going up against a monster that he's not sure he can adequately protect himself against. So, he chooses to drop his off-hand attacks to +7/+2 and boost his AC by +5. His primary weapon's attacks become +10/+5/+0.
If he gets an attack of opportunity after his turn this round but before his next turn next round, he uses the weapon he's using offensively (in the example case, +10) to make that attack of opportunity.