The fact you list 3 examples of the concept pretty much explains through its existence why that wouldn’t happen.
Regardless, @TeslaEffect
Perhaps dropping the humanoid forms would be for the best, and have the colossus be animalistic machines, it would ultimately result in a better set, we all know what most transforming Lego sets look like, gappy and stiff, I would suggest perhaps being able to separate the colossi into chunks and mixing and combining the parts, ultimately forming either two kaita or a larger singular kaita nui.
I suggested they be powered by elemental energy, both as a way to balance the power boost, but also it could explain why they were lost to the tribes, as they were unnecessary and unwieldy given the matoran’s limited elemental ability.
Either way, I’m in agreement that the kaita and exo-toa should be merged.