Player's are able to be a human and other kinds of animals (note this needs to be taken into account as dressing up animals who have different room for hats and hairstyles, for example, could be trickyish). Player's are able to use whatever gender and pronouns they wish, and are able to edit this at any time, easily.
Game has to be easy to mod. For example:
In addition to the regular mode there could be town and home design modes, where everything is available and players can create whatever, AKA 'creative modes'.