I personally think that story progression is one of those things where extensive customization options are a must. I prefer a rotational style where I play puppet master in the lives of my sims, so I don't appreciate the game deciding to pair my sims up with unapproved partners or giving them kids I don't want them having. To me, that's the game playing itself, and it takes all of the fun out of things for me. Others, I understand, aren't such control freaks as I am and like the game to play itself because they like surprises. Both crowds can be appeased with plenty of options for story progression.
Autonomous Romance: High, Moderate, Low, and Off
Autonomous Marriage: High, Moderate, Low, and Off
Autonomous Kids: High, Moderate, Low, and Off
Autonomous Moving: High, Moderate, Low, and Off
...And so forth, with separate toggles for played and unplayed households for full customization. So, say, someone who doesn't want their own played sims to be messed with by the game, but doesn't care what the game does with the NPC's can turn off all of those story progression options for their played households, but turn them on High for the NPC's.
TS4 is very, very short on save set-up options without a mod like MCCC. That's a huge shame, because it makes every player frustrated; freewheeling story progression lovers, rotational control freaks like me, and everyone in between.
