what about, on a certain day of the month, this npc appears to change some genderless Pokemon (this can be considered an event) and asking in return some random Pokemon. So, in this period (24 hours / 2 days / anyway) players will look for that Pokémon to breed and change as often as he deems necessary. A small example: -npc: Oooh, look what I have here, a Staryu, but I love to have a jigglypuff, you happen to have one? So this one day of the month, we will have an "event" where all players who want to have a competitive Starmie, seeking a jigglypuff modest/timid with ivs he can. So we still have some difficulty in getting Pokemon with some Hidden Power, but not everything has to be so easy.