Takanuva's could use his light power to create laser beams that could slice through protosteel.
A Toa of Light was the ultimate weapon against beings of shadow such as the Makuta. Takanuva could temporarily blind an opponent with a flare.
No lone Toa could defeat a Makuta except for a Toa of Light.
Tapping into one's inner light would not suddenly turn oneself into someone with Toa of Light powers. At best, one would be able to hurl a light blast like Av-Matoran could.