5 years after the end of the 14 machine war, Yorha starts the long effort of rebuilding earth for mankind. When suddenly a new threats comes to their world. (Slight different ending of Nier automate and head-cannon. Slight OP Yorha.)

Side story of Children of Humanity- After uniting Androids and Machines, the Union of Earth and Artemis continues its steady expansion across the stars...

After the end of the 14th Machine War, the survivors now look to expand to the stars... and a not-too-welcoming galaxy (This is obviously set anachronistically. Although first contact with any Council races will be in 11,983, in the form of pirates in the Attican Traverse, the galaxy will be roughly based on the Citadel Council in the 2100s...roughly)

Over two centuries after the Union's Ambrian Traverse Expedition secretly left for the Large Magellan Cloud, Kino-221 is among a number of scouts dispatched in an attempt to discern the situation in the Milky Way... Sequel spin-off of Children of Humanity

Just an idea I hope someone takes advantage of.

Humanity is gone. Cut short before they ever had the chance to leave the cradle of their home world. Though they have perished, their works, their creations, and perhaps even more; have lived on after them. What now lay before them was a future among the stars, delayed but not abandoned. (Mass Effect/Nier: Automata Crossover/Fusion)

More than two hundred years after the 14th Machine War, the androids of Earth continue to follow the final orders of their creators, marching ruthlessly across the stars at breakneck speeds. However, as they meet a galactic civilization undergoing a turbulent change, they face their first test as sapient beings... WARNING: Heavy Spoilers for NieR: Automata!