Seeing as how you can change the attack target to a "Command Knight" when you have another monster on the field, I'd have to say you could switch the target to a face-down monster, and then the effect of "Brain Control" would simply disappear since it can't control a face-down monster. It would be similar to chaining "Book of Moon" to "Brain Control" to bypass it's effect.
Sorry, Simon. I'm going to have to contend with you a little on this one. You can switch the attack target to "Command Knight" because ONLY your opponent is disallowed to sellect "Command Knight" as an Attack Target, the controller of "Command Knight" can select it as an Attack Target, if (s)he so desires. I would put Shift in the same catagory as Patrician of Darkness--Only LEGAL targets (and it is illegal to equip a Face-down card):
Patrician of Darkness
Effect Monster (Zombie / DARK / 5 Stars / ATK 2000 / DEF 1400)
As long as this monster remains face-up on the field, the controller of this card selects the targets of their opponent's attacks.
RONIN:
1. For this card's effect, the chosen attack target must still be legal. You cannot force a monster to attack directly if it normally cannot, or force a monster to attack a monster on its own side of the field.
2. The effect of "Patrician of Darkness" does not override the effects of "Marauding Captain", "The Legendary Fisherman", "Solar Flare Dragon", etc. You cannot choose an attack target prevented by the effects of these cards. Examples: You cannot choose "The Legendary Fisherman" as an attack target if "Umi" is on the field. You cannot choose another Warrior-Type monster as an attack target when you control "Marauding Captain".
4. If a monster has the optional effect of attacking directly, such as "Rainbow Flower", you may choose a monster as an attack, or a direct attack.
5. When you control "Patrician of Darkness" and a monster equipped with "Ring of Magnetism" you must chose the equipped monster as the attack target.
9. [Re: Command Knight] If you control "Patrician of Darkness" and "Command Knight", and your opponent attacks, you cannot choose the "Command Knight" as the attack target.
11. [Re: Inaba White Rabbit] This card can only attack Life Points directly. It cannot attack another monster. If the opponent controls "Patrician of Darkness" and you attack with "Inaba White Rabbit", it is still a direct attack; they cannot select a monster as the attack target.
13. [Re: Raregold Armor] If you control "Patrician of Darkness" and have a monster equipped with "Raregold Armor", you can only re-direct attacks to the monster equipped with "Raregold Armor" as it is the only legal target.