Hm, alright then.
In that case, I propose the Archatype for making 2 weapons you can customize and alter instead of one for soul knife, and then that feat to let them stack with a Martial Adept for advancing 1 or 2 key class features and psionic Manifesting/Martial Maneuver advancement.
That would be the TWF feat that would actually make TWF every inch as good as THF.