We already have 'heroic' Sinestros - Sinestro himself, for instance.
He's a pretty solid Well Intentioned Extremist, perhaps even a Knight Templar - he's doing what he does for (what he sees as) an ultimate good - forcing the Guardians to become straight up tyrants to crush chaos, and disorder.
As a consequence of who's in charge, that's pretty much as close as we'll get to truly heroic types in the Sinestros - anyone who tries to go against Sinestro's view - or, now, Mongul's - will be removed (mercilessly purged, most likely). The Greens are in the same boat (though are less likely to go a violent route in removing the bad seeds).
The only Corps whose nature really lends itself to successful dissent within the ranks would be the Blues and Indigos - in addition to the above, Red takes over entirely, the Sapphires are given to forced indoctrination, and Orange is only one person. Indigo, on the other hand, lends itself well to the Well Intentioned Extremist, and Blue could range anywhere from as passive as Hal accuses them of being, or the kind who try to actively try to make their hope come true.