How about an Egyptian period?
Allowed: Ground, ghost, normal, bug, poison and flying.
Banned: Water, electric, and steel.
Mandatory: Cat, Beetle, Snake, and Bird.
Added rules: Sphinx Rule: At least half of your Pokemon cannot have a visible nose. Slave rule: You are a slave building a pyramid. You have no money, only the stuff you find.
2nd Gen: Fighting is allowed (rebellion).
I think that this could be an interesting addition.