I am by far not the first person to have noticed some trans subtext surrounding Takanuva. He was believed to be a ta-matoran (matoran of fire), despite truly being an av-matoran (matoran of light). Along with this, as a matoran, he wore a blue mask, the shade of which being a color associated with female matoran. Later on, he fully realizes and accepts who he truly is and becomes a toa. When he becomes a toa, he changes his name to Takanuva. It should be noted that, as far as canon goes, Takanuva is the only toa to change their name upon becoming a toa. To summarize what happened, he realized and accepted who he was and got a new body and changed his name.
I may have missed a few things, but I feel like that's a decent summary of the subtext.