That would prevent Shido from gaining power and thus make it so Joker would never get arrested. Thus, he would not become a Phantom Thief and Igor could easily just pick someone else like Mishima, as he is already aware of Kamoshida's actions. Therefore, Akechi has no redeming qualities and could of just as easily been not included in the story. Heck, they could've just made it so that Shido had the powers of Akechi and did those crimes directly. That way, it has a more powerful effect and Atlus doesn't try and force us to simpathize with a terrorist