@ Armor Of course in the long term it is better than both bracers and mage armor, but it wasn't supposed to pass it early on. It doesn't stack with bracers in the same way bracers don't stack with armor -- that problem is already has its solution built into bracers, and very importantly, it scales off of class level not caster level, so you won't get the full benefit if you go into dragon disciple as it isn't a bloodline ability that would be increased (part of the reason we call them mutations is to make them not part of the standard bloodline ability package). You can already get that +14 natural armor bonus with a +6 armor bonus (bracers, or the enchanted armored skirt/ceremonial robes) or higher (mithral chain shirt for example). What this saves you is gold, but it saves it at the high cost of a class feature. Armor bonuses are a dime a dozen, especially without the problems of encumbrance. The encumbrance factor and the fact that armor bonuses don't stack, the fact that it scales but slowly means it is a trade off but one that does pay in late game (though not too much).
Ok, my concern was that it was a bit too much for an arcana, but I think that I am in the minority here. It won't change anything other than freeing up some gold for gish-types, and that isn't a type typically discussed when bringing up balance concerns.
@ font of ki The of font of ki was to provide some ki abilities (and ki) without it actually being something scaled to an ability. I would rather reduce the power of the font of ki, than introduce an one off mechanic to have it hit another bloodline power. The over all idea was that if you multiclassed into something with a ki pool you would gain something for your trouble (the concentration check and caster level choices as well as a few ki points... about as many as a feat) without giving the sorcerer the full range of choices other classes get. I really don't like the idea of the wisdom to ac choice. That matches the monk's abilities but not ki abilities.
Perhaps restrict the options to concentration, movement, and caster level? With the severe limitations per day, we could probably allow all of these options to be used at 1st level (I have been considering the Arcanist abilities here). How about revise to the following.
Available to: Destined, Arcane, Oni, Starsoul, Impossible, Rakshasa
Benefit: Through a natural gift of your bloodline you have learned to draw from a font of power that typically requires dedicated training and study. You gain a Ki pool of 1 point. This pool increases by 1 at 3rd level and again every three levels after 3rd. As a swift action, you may spend 1 point of ki to increase your movement speed by 20 ft for 1 round, gain a +2 bonus on concentration checks when you cast a spell defensively, or increase your caster level by 1 for 1 round.