Besides, having different starts changes the dynamics (forced vs not forced to steal that early worker is an example). It's like playing a different scenario.
Hmmm. Now that'd be interesting. For instance, difficulty level just controlling how much yields everyone gets. Then, in the settings, activate a package of challenges (AI starts with a worker, another for AI with extra explorer but ruins disabled, another with an extra settler) and those masochistic players could activate more than one challenge at once.