At some point inbetween the release of Metroid Prime and Metroid Prime 2: Echoes, a proposal document was made for 'Metroid 1.5' a prospective Retro Studios title that added multiplayer and number of new mechanics to the prime franchise. Obviously the game was never released, but you can now download the original proposal document, and it makes for some fascinating reading.
This design document was written by Tony C. Giovannini, then a level designer at Retro Studios, a developer who most recently worked on Epic Mickey. It seems that some of the ideas in the document were integrated into what eventually became Metroid Prime 2: Echoes.
This adventure would take place immediately after Samus takes off from the surface of Talon IV. Upon exiting the planets surface, Samus decides to take a long rest in her Cryo chamber as her ship autopilots home. However, something goes wrong and Samus’s ship computer hones in on a distress signal. The distress signal is coming from a huge alien vessel (huge like the size of several Star Destroyers) that is drifting out in space. As Samus’s ship approaches the alien craft, a tractor beam activates and the Ship is pulled into one of the gigantic docking bays. As the ships doors close, the gigantic vessel folds and enters a parallel dimension, thus begins Samus’s new adventure…
The story circulates around the concept of a rogue AI onboard a ship - it is Samus' goal to disable the AI, which has gone insane and splintered into four different personalities: the killer, the child, the mother and the martyr.
... the ship’s AI has gone mad and the ship is actually a war vessel that is on a collision course with a peaceful planet. It’s goal? The entire enslavement of the race of beings on said planet as well as natural resource stripping as its (the planets) destruction. So in essence, the ship AI has split into several different personalities, and is playing a deadly game with Samus. The Alien inhabitants of the ship are also in a state of suspended animation because as the ship travels through the parallel dimension, the alien inhabitants are being created and refined for warfare until the ship arrives at its destination and assaults the planet…However, the robotic and automated entities are not, these will be the primary enemies that Samus must deal with. In addition, Samus must also deal with the ships cunning AI, who will all the while be taunting her and trying to trick her at every opportunity.
If you have the time, or you happen to be a huge Metroid fan, we'd recommend reading through or at least scanning through the concept art. We'd love to see some of these ideas integrated into a new Metroid game - especially after the disappointment of Metroid: Other M.
Thanks to Mama Robotnik from Neogaf for digging this out. Awesome find.