TL;DR- Year 3 final fight with Makuta involves the Shadow Toa, which are versions of the Toa consumed by the real Toa's past turmoil and their elements. This allows Makuta to remain a "chess master" villain and not turn into a powered up brute.
After seeing @FuegoDeCera 's pitch for Toa Nui, I began to think; would Makuta have some sort of powered up form by the end of Year 3? And then it went further; with the establishment of Makuta being this behind-the-scenes plotter and manipulator, how would a final fight go down with this type of villain?
So there are these brainstorming sketches (I'm posting in case any seem more interesting than what I decided on in the end)
One idea was a mech made out of the Rahkshi, sort of a call back to G1. However, it still ended up with giant brute monster, which is against what I planned. Another was him being this floating head thing, sort of like Andross from Star Fox. And so on.
Finally, I got the idea from the first book in Bionicle, where the Toa fight shadow versions of themselves. It worked since Makuta himself wasn't actively fighting, and the sort of manipulation idea is used as he makes the Toa face their past/alternate selves.
So here they are (I used the TTV designs as templates, because lazy XD);
Shadow Tahu is a being consumed by rage and wrath. Lacking control over himself and his element, his body is deteriorating with magma. He is the Tahu that let the war get the best of him.
Shadow Kopaka is heartless; apathetic to everything and everyone, including himself. Ice has frozen his soul, and is what would've happened to Kopaka if he had isolated himself from the others completely.
Shadow Gali is extremely unhinged; while real Gali has balance between power and temperance, her shadow version is a maelstrom of sadism. She is Gali who's forgotten her past as a powerless matoran and is engrossed in her Toa power. (Her right arm is actually made out of water, her hooked hand being a trans-piece.)
Shadow Pohatu is egotistical and selfish. He is Pohatu who has never learned humility and let fame get to his head. He wears a blindfold since he's so confident in his connection with his element; he feels vibrations through the rocks beneath him to find his enemies.
Shadow Lewa is like a storm of madness; she does everything out of rashness and is very unpredictable when fighting. She has let herself be consumed by her element, resulting in the majority of her body becoming a polluted cloud. She is the Lewa who became so nihilistic that she became a chaotic tornado of destructive insanity. (She has a trans- head piece and the translucent ghost legs)
Shadow Onua is actually different compared to the other Shadow Toa. He is Onua who has become so overcome with grief that he stayed in isolation for so many years until his body deteriorated to the point of death. Now he's a lifeless husk, really only attacking due to being Makuta's creation.
In the final fight, Makuta summons these creations to fight the Toa. The Toa have difficultly fighting themselves, both unable to counter the high levels of corrupted elemental powers, and seeing their mistakes and troubled pasts embodied in physical form. They realize they need each other to win the fight, and the Toa aid one another in defeating their shadow versions. This would be vital storywise; after Year 2's civil war, the Toa probably still have rifts in between them, especially Kopaka and Tahu. With this final fight, they finally unite as one and overcome their demons (literally and metaphorically).
After the Shadow forms are defeated, Makuta goes down pretty easily. (Maybe the Toa unite into Toa Nui for the fight but that can be decided later by the cast).
Anyways, let me know what ya'll think. I know Year 3 is a whiles away but hey; it's always important to get ideas out there.