This deck was originally meant to be Lyra Dawnbringer to showcase the great synergy and power of angels. Since mono white still lacks a lot of the basic things you need from a Commander deck, we had to add Green. Mono white can't draw cards or ramp, but green gets to do both!
Shalai adds a lot of protection once you get a board of angels going, which is easy to do with all the token making. Given that white protects very well against opposing board wipes you should have no problem keeping your life totals high and opponents on the backfoot.
