By the way... did anyone else see "Chaotic Neutral rogue" as a warning signal for "sociopath fantasy"?
Yeeeeah...I've known exactly two people who could pull off the "Chaotic Neutral Rogue." The first was really playing someone like Han Solo with a playful streak and a love of shinies that could occasionally overcome her preference to avoid letting anyone suffer. The second is seriously dedicated to her craft (she'll steal from EVERYONE, doesn't matter how good/helpful/needy they are), and not at all averse to killing people who get in her way, but at the same time she has a soft spot for children and hard-luck cases and deeply respects the devotion of my Paladin.
All the other CN Rogues I've ever heard of were either comedy relief characters not meant to be seriously believed; truly Chaotic Evil people simply masquerading as Neutral so the DM wouldn't be constantly suspicious; or outright trolls whose only goal seemed to be "figure out the way to




things up the most for everyone else, do it, then giggle as they deal with the fallout."
In my perhaps-not-so-humble opinion, CN is the worst alignment in the game--even worse than the stereotypical Lawful Stupid so-called "LG" Paladin archetype. At least the Lawful Stupid Moral Policeman generally has (what he thinks is) the party's best interests in mind. The Chaotic Stupid "CN" Rogue archetype almost always thinks of nobody's interests but her own...and even that isn't always the case.
As for the OP, two simple answers.
1. Seriously, address this rape thing. People
should not have a casual attitude about rape, especially when they're making up fantasies about it. (If you've ever heard of the Penny Arcade "Dickwolves" strip,
that is where its dark humor lies: it's not, at all, that rape is funny; it's that there is black comedy in the idea that MMO players are
so desensitized to the situations they face that they can simply walk away from people CLEARLY suffering horribly because "hey man I have my quota." Rape is used
because it is actually serious, and thus the PC's response is thrown into stark relief.)
2. Personally, I love Dragonborn and most reptilian races, so I'm actually OK on a theoretical level with the idea that you can have "half-dragonborn" characters. Kobolds in particular (if you take them to be lizardy rather than doglike) make sense to me; I expect a "Koborn" to be kinda sorta like a mul from Dark Sun, being halfway between the parents' characteristics. (Working from their 4e stats, since I don't know the Kobold's 5e stats, they'd definitely have a +Cha, and probably +Con or +Dex (trading away the strength of the Dragonborn for some of the Kobold's agility). In other words, if your player is able to address this more maturely, perhaps in a sort of "Miroku"-esque way (that is, comically trying to "woo" every woman he meets, while--as a player--looking for that one woman who truly captures his heart), then I don't see any reason why that woman couldn't be a kobold or a lizard(wo)man or a half-dragon or whatever. It's not like you'd even need to actually worry about statting up their children any time soon!
As sort of an aside: I think there should be more reptilian races; for example, we can make rough everyman/gruff/small 'trinities' of races e.g. Human/Dwarf/Halfing is the "mundane" group, Elf/Goliath/Gnome is the "fey" group, and Half-Orc/Minotaur/Goblin could be another ('barbarian' maybe?). But, despite having a super clear everyman=Dragonborn and small=kobold, I've yet to see a third reptilian race that could fit between. It could be really neat! Especially if it's a gruff race that flips things around a bit, what with both Dragonborn and Kobold being more brute-force/physically inclined.