Shadow Pokémon

[JrDude]

Shadow Pokémon, regular Pokémon who have had their hearts closed, making them more powerful and have the ability to use Shadow type moves, which are super effective against every type except Pokémon who are also Shadow Pokémon. Average people cannot tell if their Pokémon is a Shadow Pokémon unless they have a certain device, except when the Pokémon is from the XD series, which changes the appearance of the Pokémon, and makes it "unable to be purified" (but actually makes it easier to purify). Barely anything is known about a Shadow Pokémon until it's heart opens up some, but it will remain a Shadow Pokémon until it is purified in a specific location (by Celebi), or a special machine is used after it's heart completely opens up.
This was used for a gimmick in 3D RPG Pokémon games where you could steal Pokémon from trainers.
But I was thinking, should this be used in the 2D games? Handheld games?
Because, this is a good amount of evil, putting logic in the series, it is unlikely that this would stay within one area of the world, it would most likely spread and be done. I was thinking it could be a small thing that sometimes happens with random trainer battles, not all of them, just some. At first I think you should not be able to tell until it attacks with a Shadow type move, then you use a machine you stole from a theif/Team Rocket of that gen (or picked up because on screen it looked like a Pokéball) to steal it. Later you could get a device from the professor of that gen or something and be able to tell right away.
It would be kinda cool if Mirror B. was in such a game as well so you could catch any Shadow Pokémon you missed, and he could also be the reason on how it spread to that region.

tl;dr Should Shadow Pokémon have a part in the Handheld Pokémon series?

[Kayo]

Maybe on one game. Not in the regular series, though. Actually, perhaps a side game. Not like Ranger or PMD, I mean the same layout as the regular games (B/W for instance), but with older pokemon (maybe) and shadow pokemon. Not like the way you said, but more like a Col/XD sequel thing... for the handheld. It could work. Really.