I just finished/caught up with the Four Lords story and after seeing it all, I'm inclined to believe that Tenzen was the Warrior of Light or at least a Warrior of Light.
-When the Four Lords in their early stages would try and speak, he could understand their words. So that must mean he had the Echo. One similar to Krile's.
-Suzaku makes mention of how we the players share the same "Blessing" that Tenzen had. I can only assume she was referring to Hydaelyn's Blessing.
-Tenzen was an extremely powerful and skilled warrior who was stronger than any man who took down gods and fought with Auspices, like we the players are doing, kinda.
-He was super kind, loving, and gentle. Always willing to help those in need and he travelled the entire world to try and help everyone.
-Based off of Suzaku's account and the memory picture we see, Tenzen died in a flash of light and sparkles, with Suzaku saying she watched the Light leave him.
All those things besides dying are exactly the same as what we are as WoLs. Which was what angered Suzaku so much. We are a "spitting image" of Tenzen which is the same thing the Alliance leaders say to us way earlier in lv15 story. That we remind them of the past WoLs they knew 5 years ago(talking about non-legacy here). I wonder, are all Warriors of Light simply reincarnations of a single person/a group of people?
Questionssss.