Put my mind to it. I think I have come up with a good unbirth focused list. It has been performing decently on ladder, and ALL of my wins have been through unbirth :D, although it is perfectly capable of winning through tempo.
https://www.bagoum.com/deckbuilder#MTozMDEsMzoyMDA1OSwzOjExMDk4LDM6MjAwNDksMzoxMTEyMywzOjM1MSwzOjExMTI2LDM6MjAzNDgsMzoyMDA1NywzOjM0MSwzOjMwMDM5LDM6MTEwNjQsMzoxMTExMiwzOjMxNA==
Still working on it. Probably still not an S rank list, but it might be highly competitive. Between celebrant and darkfire we very consistently get those turn two 5+ mana plays allowing us to play under BOA/Sandswhirl which is the bane of most ramp lists. We sport 2.25 sources of rush for chakram/unbirth abuse (Kron requires some luck to get rush out of). Kron and or Chakram give magmar a pretty hard time, and putting the focus in the midgame lets us play around other transforms/dispels without to much tempo loss. We have a dab of healing with deso, and between deso/rep/medium curve we do alright on card advantage.