@Meddler: Does built-in gold-generation mean a Champion's late-game must be weak?

When looking at TF, GP, and Draven, all of them have varying degrees of late-game fall-off because they can finish kits faster than others. I'm in the middle of making a thief Champion who has a seriously risky means of bonus gold generation and weak early game, but has a devastatingly powerful late-game.

Is my design flawed? Is it required that if a Champion has bonus gold generation, they must have a weaker late-game?

For more context: http://boards.na.leagueoflegends.com/en/c/skin-champion-concepts/gEIw1dEE-severa-the-princess-of-thieves