Hmmmmmmmmm, I do like the class and the discipline lots, but I think we could do a bit better in terms of discipline customization for the class to make it a little bit different from the other homebrew class that does maneuvers and incarnum (The Demented One's Soul Disciple).

How about dropping Iron Heart, to leave that solely to Warblades and the like, and having the last discipline be chosen for you based on your race?

I'll start with a few pairings.

Elf: Dancing Leaf Discipline
Human: Any one discipline that isn't class-specific
Half-Orc: Army of One
Dwarf: Stone Dragon
Half Elf: Scarlet Bravura
Gnome: Shadow Hand
Halfling: Setting Sun

Shifter: Tiger Claw
Kalashtar: Sleeping Goddess
Warforged: Jade Throne