Sharpa is actually Polo's daughter.
The "classified reasons" Sharpa thinks she couldn't beat Polo in a fight is because everything she knows, Polo taught her. It's also the reason she knows there are classified reasons in the first place.The final chapter will be the rematch between Polo and Rokoa.
And one will die.Arza does not have Penn's best interests at heart.
This assumes he authored the Belenos sim in Unnatural Selection (which seems likely, given that he placed an avatar of himself in a key role). In the sim, the Sapphire Emperor was portrayed as the most villainous of the emperors. Since Penn is associated with the emperor, this could reveal his real feelings towards her. However, it is also possible that the sim was adhering to historical accuracy, and/or that Arza does not want Penn to become the next Sapphire Emperor.