System Design Ideals, some guiding principles

Small Sized Character Sheet

I want all the key information to fit in half the letter size character sheet. I want nice statement sized booklet whose pages I can fill slowly.

Easilly Expandable DIY notebook format, with Cards

I want to be able to have a notebook where I can put in cards that condense details that come up on specific occasions. Details like other entities, contingency plans and maneuvers, and other details that reward development and forethought with minor but tangible game effects. 

Complexity is Simplified in an elegant and telescopic method.
You can easily dig deeper and find more details, or you can pull back and play at a macro level.

Simplicity 

Characters can be made complex by the open ended detailing mechanics, but the core system is simple and keeps to a finite amount of elements. Typically characters are made up of 10-15 skills, with 15 a rare type of character that tends to specialize in generalization.
The Character Abilities are simple and keep in mind mnemonics to allow better memory and acquisition of system mastery.

Efficiency

What ever on the charactersheet come into play, (except the cards or the other pages). This goes for disadvantages or drawbacks traits. If you have a drawback it comes up every game, at least coloring EVERY SCENE.
Same goes with skills and other character elements, these all color the character's scene. Because the system does this, characters with subtle differences can stand out more. Anyway the rule of 7 on average skills make a profession, while 3-8 make the personality helps a lot in efficiency.

Character creation takes up 10mins, while character detail is its own game in itself.
Character detailing mechanics is a modular system that allows for the creation of character cards that will help the player in the game, a little bit like a board game. These cards are made with the permission of the GM, and to a certain limit. They detail the character and allow for some feats to be done. It grants tangible bonus on a circumstance.

Traits should only have a max of 7 both good and bad or limiting Traits. These traits should be a list easy to read and easy to recall, so that we don't forget they can be put into play. Note that elaboration and detailing has a system mechanic of its own, that allow for greater detail for these traits without occupying valuable attention unless its needed and makes things interesting.

Make a game for the Gamers and not the Assburgers

Anyone can twist a game to what it is not intended, but you want a well design game to reduce arguments and speed the decision making process, and to make everything more fun. The system should reward role-playing, elaboration, visualization, immersion, and all the activities that make a game a more rewarding experience. This may mean allowing creativity to breach the secure walls of well designed mechanics, but the guiding principle is that the people who will enjoy the game more should not be limited by the problematic people who will try to ruin the fun for everyone.

Similar principle in making laws (a game theory based principle): don't make laws for the Criminals, make laws to protect, empower, and serve the Citizens (thats why policy makers need to learn economics and behavioral economics, and happen to be a person with a lot of common good balance). Empower the citizens so that it would be harder for the criminals to abuse the system. Especially for RPGs, where the states are our free time.

Accept System Growth and Evolution

I guess the way people develop better and better software is a great example of how to develop an RPG. You document you progress and you adopt innovation when you can measure empirically the benefits vs the trade-offs.

I guess in the end, such a game system will be like a Web based comic or Open Source Software - funded by the merchandise and donations, break even when hosting events and major marketing exercises.

Prevent Mechanics Inflation

Discussed in a different post, inflation happens a lot in Game Systems. We don't notice it but in level based systems, additional powers and abilities every level despite rising XP cost actually accounts for a high power level inflation. 

This also happens in game system inflation, with added options in One Sphere (combat, social, problem solving, logistics etc..) all other spheres suffer. I think it should be a balanced approach, when we grow with options in one medium, other mediums are encouraged. 

keep inflation in sustainable levels, options grow over time as new ways of problem solving and simulating or modeling actions naturally grow because of how we form ideas. Its just we need to reign it in.