Most gamers, when they ask what a system is like, mean "What's the task/conflict resolution system like?" To me, the resolution mechanics are peripheral. The most important part of any system to me is chargen and character advancement.
In most games, those are two completely different things, totally unrelated. You roll/pick your stas & skills, equip your character, and play. To me, they are inextricably linked. It all ties back to two games which I consider the most personally influential and also most innovative - remember yesterdays post? I mean innovative like that! - game designs ever; Traveller and King Arthur Pendragon.
Among other things, Traveller introduced the concept of Lifepath character generation. Your character took on a profession which taught certain skills. Each time period you spent in generation, you rolled what skill or bonus you received that time period. Character generation ended when you retired, after which advancement, if any, was up to the GM.
Also among other things, Pendragon introduced the concept of a yearly cycle. You went out and adventured each spring, and returned home in the fall to take care of the home front. Everything was year-based - you knew how old you were, how old your children were, and your wife. You advanced your character each year, becoming more skilled, more powerful, and more famous.
I loved this!
When I designed my first game, I combined the two. Now both chargen and advancement were year based. You could stop chargen at any point, play out a year or two, chargen another few years, and play five more. This sub-system pretty much defines my games. The entire meta-system framework revolves around it. I started with random chargen, then mixed in point-buy for stats and background, and then introduced template characters, but all go through that yearly cycle. Among other things it makes flashbacks a snap.
So, a development of existing tools - no innovation for me!