Sneak attacking and Gestalt issues

[Suddo]

Swashbuckler // Spellthief
Rogue // Wizard
Do that till the end. (Maybe a PrC or something too)

The two feats that fuel this are Master Spellthief and the Swashbuckler and rogue stack for stuff. This should make you only make you slightly SAD (Int > Dex > Con). If you can get Lesser Tiefling it will help a lot.

Oh and Psychic Rogue is pretty sweet. Though I don't know if it works with Swashbuckler but you should be able to do something like:
Psychic Rogue // Wizard
Psychic Rogue // Master Spellthief
Psychic Rogue // Wizard
That to the end, probably PrCing the Wizard side.

Edit: And I think they stack no matter what when you get them so. Its +1d6 not 1d6 Sneak Attack.