God Mazinger (Original Concept)

The God Mazinger prior to any present day developments is a name used to describe an idea of an upgraded Mazinger Z. Originally beginning as an early concept on what became the Great Mazinger, the name has been used throughout productions as a placeholder before any other title becomes set in stone.

Great Mazinger Prototype
An early concept version of Great Mazinger was called God Mazinger, and featured a drastically different color scheme. Unlike the normal black, white, red, and dark blue color scheme this model bore a mostly red body, yellow accessories, white body sections, light blue horns, a black pelvis area, light green eyes, and dark green wings.

Series Project
Prior to Grendizer, there were plans for a Great Mazinger sequel where the characters continued the fight with all of the remnants of the Mycenae Empire with the Great Mazinger being destroyed, Tetsuya Tsurugi being paralyzed, and Jun Hono dying. It also featured a new Mazinger robot dubbed God Mazinger, which would have been made by a new type of Super Alloy Z known as Super Alloy God Z made from the Japanium being irradiated by anti-proton energy during the purification process, creating a much stronger metal. The Photonic Energy would have replaced by anti-proton energy. The origins of the Mycenae Empire would also be revealed as their scientists and generals being descendants of aliens. The Mycenae would also have another replacement for the Great General position known as Albatros. Unfortunately, the design for the God Mazinger proved to be a failure and the project was aborted.

Second Attempt
There was another attempt made for the God Mazinger around the late 1980's, this time as an animated movie that featured the mecha combining with an aircraft, taking notable inspiration from Grendizer along with Gattaiger. The plot of the movie would be set in the future, and would not feature any other previously established Mazinger supporting characters, but that aside, nothing else was described about it.

Legacy
With both attempts failing, the title and robot of God Mazinger was used for a series unrelated to its predecessors with a different cast of characters and plot. The use of a superior successor to both Mazinger Z and Great Mazinger was used eventually for the concept of Mazinkaiser. Other times, the name God Mazinger would appear again for an upgraded Mazinger Z unrelated to Kaiser.

Source

 * Ameba user Steamed bun
 * Twitter user @nanashiborger