This is my favorite theory, mostly because it would "rhyme" with G1's reveal, in the sense that the big good/bad ends up being the big bad/good (Ex: Makuta taking control of Mata Nui's body when everyone thought awakening him would bring peace). Imagine how shocked everyone would be if it turned out Ekimu was the one who summoned the Toa and led them on the false pretenses that they were saving Okoto, but they were actually collecting the masks for Ekimu so he could use all of them to take over the island. Meanwhile, Makuta was actually living in a self-imposed exile after he sealed Ekimu away because he felt he had failed the Okotoans, and the Toa have to find him since he's their last chance to stop Ekimu and save the island. It would rhyme with G1 without being a total rehash. I would think that instead of just a self-imposed exile, all the things like the Skull Spiders and Skull Everythings are actually servants of Makuta, so that the masks wouldn't fall into Ekimu's hands. It's a severe case of Ididwhatihadtodoeosis.