Is MCC allowed for the story progression elements so the town doesn't die out after the first few generations?
No mods allowed in you are going for the Hall of Fame.
Mods, Cheats, and Custom/Premium Content List of Approved Mods
Custom Content and Premium Content are fine and are to be used at your own risk. No mods or cheats are allowed with a few exceptions: lighting mods that change the look of the game are fine; Moveobjects is fine; some bugs may creep up that a mod could fix, but team permission is always necessary in these cases.
ResetSim Firstname Lastname. You may only use this cheat in the event of a stuck Sim.
Moveobjects. You are allowed to use this cheat at your discretion.
Buydebug cheat (bb.showhiddenobjects) is banned.
The Manage Worlds screen is off-limits unless you need to evict ghosts from households or re-populate town (more rules below).
You are allowed to re-populate your town ONCE per dynasty.
Move-in Sims can be a mixture of YA and/or children. They can be EA created Sims and/or Sims created from scratch in CAS with a blank slate - no rewards/skills, etc.
You must have at least one bad trait (mean, evil, glutton, insane, lazy, slob, hates children, jealous, noncommittal, squeamish, and unflirty) for each created Sim.
If you are moving in Maxis/EA generated families, leave their traits alone.
You can move in a maximum of 20 Sims, the household number does not matter.
Gallery Sims from other players are not allowed.