I liked how they mixed up the otherwise balance of the elements. In the main story, all the tribes were basically equal. Onu-Koro wasn't any more or less important than Le-Koro, and they were all on the same side, and all had similar political relevance. It was symmetrical.
But on Bara Magna, there's much less symmetry. All of the tribes are at odds to some extent or another, with varying alliances and rivalries. The Rock Tribe is a completely different species. Sand Tribe got blasted back to the Stone Age, in exchange for some extra limbs apparently. The Red One, Malum, wasn't even a Glatorian and wasn't even a main character.
I really wish the Bara Magna arc could have had the time to be fully developed. So much potential to revamp Bionicle. It was really interesting until Mata Nui showed up. I just know that the story team was ready to go Insaneo Style with a whole new world full of opportunities.