Speaking of video game concept documents, a rough plan for an unmade Metroid Prime installment from 2002 has allegedly surfaced online courtesy of a designer at Retro Studios.  Set immediately after the first Metroid Prime title, this adventure focuses more on solving puzzles than traditional combat as heroine Samus Aran is trapped aboard an alien spaceship drifting in another dimension (don't you just hate when that happens?).  Game Informer has the details.

Throughout the course of the adventure, Samus would be taunted and hunted by the ship's evil AI program. Samus would maintain all of her powers from Metroid Prime, but the AI program would limit her abilities in different ways in each area.

The game world was planned to be the size of "the ruins and the mines" from Metroid Prime combined, with expanded use of scan mode and ball mode. Interestingly, the document pegs the game as "more about solving puzzles" -- essentially the opposite of Metroid Prime 2: Echoes, which ended up being more combat-heavy than the rest of the series.

It certainly sounds like an interesting concept, and goodness knows that I prefer solving puzzles over being swarmed by alien beasties when it comes to Metroid adventures.  The Metroid Prime follow-up that Retro and Nintendo actually made, Metroid Prime 2: Echoes, had way too much frenzied combat for me to enjoy it.  Meanwhile, plenty of people are snarking that this unmade concept sounds better than the maligned Metroid: Other M, but there are some similarities between the two.  Both concepts involve Samus being trapped on a ship, both include the notion that her Power Suit abilities have been restricted at the whim of an off-screen voice, etc.  Say what you will about Other M, but I think I'd rather stick with the devil we know.  If you'd like to read more about this Metroid concept, NeoGAF has detailed summaries and discussion while the Metroid Wikia has the entire document.