I always thought that the whole concept of Shadow Matoran during 2008 was really bland. A leech attaches on to them and drains their "inner light" and suddenly they're evil and a flying thing has to scream at them so they can be good again and yes right okay
Wouldn't it have been more interesting if the Makuta had come in and like persuaded them to abandon their faith in Mata Nui? Which I suppose would have been hard right after Matoro used the MoLife to resurrect Mata Nui, but disillusionment with Mata Nui is something that 2006 and 2007 dealt with or at least touched upon in some aspect. And it would have been more emotionally resonant if the Shadow Matoran fought the Av-Matoran of their own free will for something they actually believed in rather than the Makuta turning them purely evil and that's that.
Just a thought.