I propose the following to start:
1. Thou shalt not do Crossovers. Bringing in one character seems harmless, but brings in a whole set of predetermined lore that probably doesn't fit.
Note: Individual elements may be alright.
Generic Werewolves = OK.
Twilight's Jacob = BAD.
Magic Spells = OK
Dr Strange = BAD
2. Thou shalt not be more powerful, or nearly as powerful as Sailor Moon, Galaxia or Cosmos.
3. Thou senshi and knights shalt be a gemstone, be in cannon, or be already in cannon. Diamond = Good. Mars = Good. Sol/Earth = BAD.
4. Thous family ties shalt not turn cannon character's into whores! Check to see who they've already been paired off to.
5. Thou shalt not be the one on the right!:
