I have been waiting patiently for an interesting unleash card without complaint but seeing a second rare that is totally bland like this is pretty disappointing...
I have to reccomend not doing this. I have a friend at my lgs who built exactly what you described and it was one of the least fun games of commander we had all done. It finally ended when we just ganged up on him and he couldn't steal enough of our stuff. Every time you play the deck you will probably be hated out.
I doubt it since it wasn't in the original Ravnica and has no reason to come back now other than being g/b. Also, this should probably have been posted in the baseless speculation thread..
What about riku of the two reflections? He can double your mana lords and your fireballs, helping on both ends of your game plan. On top of that he gives you access to red's fireballs and bkue's card draw!
The commander of the ninja plane chase 2 deck is pretty good if you can get enough guys out. Darksteel forge works in the right deck. Avacyn is an obvious inclusion. Dauntless escort and loxodon hierarch are both great although hierarch doesn't help against wraths that stop regeneration. Lastly, counterspells for their wraths will probably make them think twice before they try to nuke the board.
You should definitely try to make sure that the majority of your sac outlets are lands so that a: they are harder to hit and b: don't get nuked. The title should be, "cards that go WELL with child." Sorry, I had to get that last part off of my chest.
I don't like planar cleansing in the list. Triple white can be an issue sometimes and since te deck is aggressive, having another dead card in your opening hand that sets you back to square one just doesn't seem correct.
Chronomaton was amazing both in being a superb one drop, scaling to monster size when you need it to be, and having the best name in the set (chronomnomnomnomaton).
Coming this holiday season.