If we're operating under the assumption that Weapon Versatility changes the type of the weapon and not simply the type of damage that it deals, then the value of a feat like Slashing Grace is somewhat diminished as you can pick up any one handed weapon you want and turn it into a piercing weapon with a swift action. At which point Earth Breaker + Weapon Versatility allows you to make the Earth Breaker do piercing damage and benefit from your Swashbuckler abilities. Thunder and Fang still does not work though, as you cannot have anything other than a buckler in your off hand. At which point you'd need a Titan Mauler dip to use a two handed weapon in one hand...
