Relic Castle

Is it possible to control which Pokémon the player will encounter next while walking through tall grass? For example, as long as a certain switch is active, the player can only encounter Pikachu in the tall grass on this map.

One possible way I could imagine would be to have multiple encounter tables for the same map and switch between them with switches and variables, but I have no idea if and how that could be done and the wiki even states "a map's section cannot have more than one of the same encounter type".