There is one factor that causes what's going into GMS and what into AOSP, that the article conveniently glosses over:
Functionality in GMS requries server side support. It can be computational capacity or server-side dabatases (fused location with wifi and cell towers? Google caller id? Map tiles? Storage? Server side push? Cloud support for games? All of them require something on the other side of connection).
Unless someone is willing to step in and provide this, there will be no AOSP equivalent.
Launcher certainly does - where do you think that Google Now prepares it's data?
Launcher without Google Now is part of AOSP.
Both Calendar and Email are available in AOSP, Play Store has their binary builds for those that for some reason do not have current Android version. They can have at least current apps.
Functionality in GMS requries server side support. It can be computational capacity or server-side dabatases (fused location with wifi and cell towers? Google caller id? Map tiles? Storage? Server side push? Cloud support for games? All of them require something on the other side of connection).
Unless someone is willing to step in and provide this, there will be no AOSP equivalent.