The decision to go with EVIL is pretty exciting. It's a good time to do some interesting stuff while other promotions are sitting pretty. EVIL's only 33 years old. It's a big push up the card and I'm sure people will remember it, even if he doesn't become a permanent player like Okada, Tanahashi, Naito, etc. But it feels interesting, and he might just stick. Now he's actually a triple champion, isn't he? That makes him seem even more special, even if just for a fleeting moment in time.
And it makes sense to put him over to make the New Japan Cup consequential in later years, and to really sell EVIL's turn. Gedo is pretty good at making wrestlers who go into business for themselves stand out for a while to make their turns more effective. He's made stars out of Okada and White by joining up with them, and now EVIL's turned heel and joined the BC and it's worked out for him too.