I have a game design I eventually want to make...but I'm too afraid to put it here or anywhere else (mostly out of fear the Idea will probably get stolen

). But what the hey, can't make an omelette without breaking a few eggs as they say.
The entire idea is grand and probably unfeasable due to just the incredible
size of it. It would require either an engine so moddable that it could seamlessly do FPS style gaming ala Half-Life and maybe BF2, RTT-Style gaming ala WiC (except with a bit of base building involved), Flight-Sim like Freespace or maybe I-War and finally Ship-tactics like in Jupiter: The Nexus Incident. The most ideal solution would be to have two or three different engines to handle everything.
The reason for this is simple enough: the basic premise was not to have a single game or story - but rather, seven viewpoints to a single story.
The story premise is sci-fi and is centered around the a mysterious AI known simply as Celeste. Players get to choose from six different characters; each one that has been affected in a different way by the main character - but more importantly, each one is a different viewpoint in the same universe (but with different stories). So while you may play through certain places in Character A and receiving orders from command, in Character B you get to BE command, giving those same orders to the other character. But at the same time, you can go behind the scenes in Character C, influencing some of the decisions that led up to those same orders. The seventh character to this would be a secret unlock, which followed Celeste's storyline more closely in the form of a reporter that is hunting for clues on unlocking the mystery.
This level of connection would be present all over - but yet at the same time be exactly that: connections between seven unique, incredibly different stories. And if that isn't enough, consider this: each one has a different style of play. Character A could be little more than a grunt, playing in your traditional FPS-style combat sent in to 'clean up' an incident that involved the AI. Character B would be a General, playing a top-down RTS on one of the planets as he dealt with the AI's sudden influence and aid to a rebellion on his planet. Character C, a ship captain, would have to deal almost directly with the resulting fallout of the planet's decline into war as the conflict came into space; fighting almost directly with the AI - so on and so forth for each character.
But it doesn't end there either. In each of the modes of play, everything is customizable. In the FPS mode, the weapons can be built up from scratch, much akin to Gal Civ 2 - even better though, is that you can literally customize their purpose in real-time. Shotgun-Rocket Launcher? Mix the two modules together. Want a fist-sized artillery barrage? Fix a artillery module onto your tank. Want shields that are strong enough to ram an enemy ship? Put in a power plant, big-ass engines and go! This would apply even to cosmetic designs. Although default designs would be there, if you wanted to customize your ship of terror, your units, or even just pimp out a shotgun you could do so with decals and the like (similar to Chromehounds). Of course, such degrees of customization would only probably be available for those that really want it - a simple interface could pump out quick, easy designs without any hassle for those that just want to get into the game and play.
The story would also have an RPG-like atmosphere for some of the characters, holding potentials for multiple endings to that story arc as well as the traditional skill-trees to match playing styles; although this would be flexible with lines blurring between any set 'classes' as you could literally do a mediocre jack-of-all-trades if you liked. Even for arcs that dont have multiple endings, linearity would serve to move along the story and focus more on the gameplay and fun elements than anything else.
There's a bunch more stuff; but that's pretty much the meat of the entire thing right there. Sorry for the huge blocks of text which nobody would probably read XP