Perhaps because of the Peacekeepers, the morality and honesty of the people will end up falling to the point that they would not even be able to make a scandal, I also think it unlikely that Rose will end up becoming a public slut, perhaps she will end up becoming a slut for nobles.
Unless I'm missing something I don't recall it ever being said that the Peacekeepers are what keep the people from being sluts. And again, the Duke feels like an extremely possessive character. In my mind it's far more likely that he collects all of the women in Leto's life for himself instead of letting any of them being shared around.
In terms of the franchise being depressing... yeah, the HC games are kinda harsh. HC3 feels like it's bucking the trend, but at some point Leto has to start to realize he's losing before he can either lose, win, or win harder. On the plus side there's typically an ending in which the MC gets to live out the power fantasy and in the case of HC3 no one is sucking any dicks in a misguided attempt to protect Leto.
I'm firmly of the believe that the problem with HC1 and 2 is that the games go out of their way to emasculate their main characters. The main character of HC1 is an absolute dickless wonder. He's shat on basically left, right, and centre. By the time he clues in he's been in the presence of all sorts of horrors and since he's a butler of the manor he probably had to clean up the splooge of the demons taking the female lead and his sister, at the very least he unintentionally assisted himself in getting cucked, and by the end of the day he required literal deus ex machina to save the day. In the case of Noah from HC2, well, that one hurts more because Noah isn't ever given a chance to be anything. He's lied to, belittled, and sabotaged from the get go, his mother and the woman who claims to love him both fuck around like crazy and even justify it as being done to protect him even though they never truly believed in him and never really gave him a chance to stand up for himself. Even Noah's revenge ending victory is again gained with deus ex machina and centres around him getting the sloppy seconds of everyone else in the village.
Leto seems more confident, seems more competent, seems to be upwardly mobile, and more intelligent than his predecessors, but N_Taii mentioned in a comment on his patreon that taking the NTR route will cause him to become pathetic, thus possibly leading him down the same path as Noah. Which would be a shame. However if there are no gods involved this time around the good endings will be more satisfying and therefore more enjoyable. Hard to say, but regardless I do like the sprite work.