>>29942497Bringing Celebi and Dialga to a specific location allows secret time travelling like Lake of Suune and Moone for fossils or starters.
Held items, abilities and leading Pokemon influence what is seen.
Eg Berries attracts more flying types or maybe just elemental flutes or something which increases the frequency of seeing stuff in the wild. Or glasses that enable you to see extra Pokemon.
Pokemon can affect the wild too.
Eg Leading with Kyogre causes more water Pokemon to appear. Leading with Groudon leads more ground/fire Pokemon to appear. Jirachi gets three wishes (encounters, items etc)
Snag balls. They're a good way of reducing encounter table expansion. So, say that the time travelling mentioned earlier allows (you) to snag the trainer's Pokemon from early game.
Finally, Pokemon Super Mystery Dungeon style quests for recruiting Pokemon rather than awful overpowered giftmon.