My guess is that Piras is like the enforcer for the higher order lawmakers, or something like that. Much like Ultra Magnus in TF: MTMTE, he'll be the "Duly Appointed Enforcer of the (insert law/act here)".
For all we know, he could be a villain in a whole different way. Maybe he will end up supporting a government that shows the Matoran some love on the outside, but the Toa Novus find out that the inner workings of the government really hate the Matoran and are using the Toa Miro as puppets.
Either way, I know this is going to be good.