Considering what darkshade said about recognizing the pokemons as "drops" if we were to regard them as item drops on an mmorpg level, either you re-obtain the requirements or trade with a person. Finding a shiny is hard enough, also regarding the method of how yo obtain a shedinja, the grinding will be too irritating, for that i agree with the idea. Also to think that it would create an opening in the market where players will actually need to trade if they were unsatisfied with the shiny they obtain. As for an example to that; on a regular mmorpg game there is a boss with two item drops and its highly rare to encounter. So either the player will need to re-challenge the boss and hope for the other item or trade with another player. I personally find it interesting.