-trying very hard not to comment on the "my personal test" nonesense-
This subject has been somewhat discussed before, it is more or less agreed that changing sides will never happen, we are warriors of light, we will always be warriors of light fighting for the good of Eorzea against anyone who would seek to harm it, that is the entire reason Hydaelyn chose us to have the echo.

If we switched sides to join the villans we would have the echo taken away, and would return to being ordinary people.. lol adventurers were never all-powerful just chosen and exceptional.