In my opinion, if birthing pod ever becomes as broken as survival of the fittest in some way, it will have to be run in a b/g/x deck
B provides you with a great card in bloodghast, recur for a lot of powerful 3 drops
G provides you with vengevine, which recurs for 5 drops and is a good card to be able to recur period
To see my general opinion on birthing pod go to my G/B/W birthing pod deck linked at the bottom
As for X I am going to try to make a deck with all the others for experimenting, but this one is the R splash
Red automatically adds lightning bolt, no questions asked
now for 3 drops, I find cunning sparkmage, mimic vandal, and Tuktuk the Explorer (:D)
I think i will not use sparkmage, but vandal is atleast on side to deal with swords and mimic vats (which hit this deck very hard) and i have no problem including a 3 drop that will sac to become a 5 drop, no problem at all
as far as 4 drops go, i could use Hero of Oxid Ridge, or Oxidda Scrapmelter (more artifact destruction), or maybe even Soulsurge Elemental
Now here is where things make the biggest impact, 5 drops. Why? Because the only real one I have from green and black are acidic slimes and I like 5 drops to combo with vengevine
so here are the 5 drop options: Kazuul, Tyrant of the Cliffs, Kuldotha Phoenix, Kuldotha Ringleader,
Magma Phoenix, or umbrask, the hidden
WHOA, look at all those 5 drops, here is where things get interesting, I can redo my mana curve now to fit what i want perfectly for the deck, heck do i even need a 6 drop? nope, so the slot goes to more 5 drops with haste after umbrask appears
Note, this is the first draft of the GBR version and will probably change a lot, hopefully based on your comments so I don't have to do all the work :P
Other colors (will update as they are made)
the G/W/B version is here: http://www.mtgvault.com/ViewDeck.aspx?DeckID=182316