It seems I was beaten to suggesting soulbow.
Savage Species has a magic item called necklace of natural attacks that imbues your natural weapons with the properties of a magic weapon. Since you get a custom item, ask the DM if you can get an analog of this for your mind blade. It will cost 600 gp more than two copies of the magic weapon (minus the cost of masterwork weapons) if you want to be able to use it with two-weapon fighting.
The weapon property you really want is splitting, from Champions of Ruin. This costs +3 and splits every arrow you fire into two arrows, doubling all non-precision damage. I assume this is figured into s'emaNsdrawkcaB numbers, though you actually only make one attack roll for each pair of arrows.
I'd consider spending fewer feats on two weapon fighting. You can take two-weapon fighting (with 9 dex and gloves of dexterity +6) and wear gloves of the balanced hand, from the Magic Item Compendium, which give you improved two-weapon fighting if you already have two-weapon fighting and only cost 8,000 gp. You don't get the last off-hand attack at -10, but I'm not sure that's worth two feats.
Using the guidelines for combining magic items (with updates in the Magic Item Compendium), gloves that give you +1 splitting mind arrows, +6 dexterity, and improved two-weapon fighting would cost 112,600 gp, well under the 162,000 gp of a +9 weapon.
I'd consider a divine gish for the 13 levels that aren't required to get mind arrows. Someone should have some utility magic, and you only need to lose 1 point of base attack bonus to get some decent divine casting.
