Okay, so I was thinking lately about Blood Baron of Vizkopa and it's recent decline in price due to people barely running it in any other non-standard deck. I thought about splashing black in mono-white Soul Sisters for that and Sin Collector in the sideboard.

Main Deck
4 Godless Shrine
4 Horizon Canopy
3 Marsh Flats
7 Plains
2 Swamp
4 Windbrisk Heights
2 Brave the Elements
4 Path to Exile
4 Serra Ascendant
4 Soul Warden
4 Soul's Attendant
4 Ajani's Pridemate
4 Spectral Procession
4 Ranger of Eos
3 Archangel of Thune
3 Blood Baron of Vizkopa

Sideboard
1 Brave the Elements
3 Grafdigger's Cage
2 Kor Firewalker
3 Suppression Field
2 Oblivion Ring
4 Sin Collector

Thoughts?

Your mana base is going to detract from the Serra Ascendents, making them harder to get online. I'm not sure what you're gaining is worth what you're losing.

That being said, if you're going to splash black anyway, I'd recommend Lingering Souls and Inquisition of Kozilek.