This is nothing to LOL about!
Do we want to include Fakemon?
Do we want to include Gen IV/V Pokemon?
They really depend on the story and basis of the hack. I'd say that, as a community that has general interest in fakemon (as hacks such as Sienna have proven) and the interest in gen IV/V pokemon (as numerous hacks and tutorials have proven), it would be best for us to attempt to add them both if the situation allows for it- so long as we do not remove any, or too many of, the existing pokemon.