One of the big perks of buying the Pokeball Plus assessory is that it enables you to transfer the legendary Pokemon Mew into your Pokemon Let’s Go Pikachu and Let’s Go Eevee game. Playing as the 151st Pokemon has it advantages, but deleting your Pokemon Let’s Go save file will permanently delete that Mew from existence.
Nintendo’s support page mentions that once you transfer Mew to the game, you will not be able to obtain it again on a new game from the same Pokeball Plus. Additionally, Nintendo won’t be able to replace or restore a Mew in the case it becomes missing or deleted. It’s just a one-way transfer as the same Pokeball Plus also can’t transfer Mew to another game of Let’s Go Pikachu or Let’s Go Eevee. This is likely a big reason why players won’t be able to get their Mew back if they delete their save; it’s a one-way ticket meant to ensure there is only one Mew per ball no matter what.
Some people like the idea of starting a new Pokemon game, choosing the right kind of Pokemon to start off with, then delete the saved game and then resetting if they don’t like its stats or nature. It’s a common practice for most Pokemon fans, and is also helpful for those looking for shiny variants. But you can’t do this in Let’s Go for Mew.
Purchasing another Pokeball Plus will enable you to transfer another Mew to the game. At $50, it’s a steep price to get another shot at the legendary Pokemon. The Pokeball Plus’ main function is to serve as a controller for Pokemon Let’s Go. But it also acts as a Pokemon Go Plus device, grabbing items from PokeStops as you go for a walk. You can also put a Pokemon from Let’s Go into the Pokeball, collecting experience points and items as you go for a stroll.