I actually do something similar except that I play fully as a Sith Lord.yeah tho those saves are more or less pure light saves so I resist the urge and vis versa with my dark saves. My main save is kind of in the middle like a grey jedi in a way well expect when it comes to Eliza then my MC turns into a Sith Lord.
On your first point I guess it comes down to personal taste, but it just gets frustrating with lack of choices or them having any meaning or outcome on future scenes. No matter what I choose it always plays the same so it might as well be kinetic novel. I choose as negative a choice pretty much same thing happens regardless.Personally the Royal arc is my favorite right now I think. In part because the princess is my second favorite character after this update. As she reminds alot of Eliza I consider her basically Eliza 2.0. But we saw some good deveolopment from Luna , lore building of the world and the other angels / deities as well.
I do agree the other Kingdoms are far more interesting but I really get the feeling that is done on purpose. As I assume the MC is going to be a protector of the realm of sorts against these other kingdoms either as a ruler or just simply helping out the Royal Family in one way or another.
I do disagree about revealing to the King we are a Nephilim as a show of force to not fuck with us instead of being sent to the dungeons. To me that would only make sense as a Dark Option. I wouldn't want to do it on a save im not doing playing purely on the dark path as my main save. As I still consider the Royal Family my allies they were just manipulated by Taron. Not just that im under the assumption we are not trying to reveal to others we are a Nephilim. Even with a show of force I wouldn't trust the guards not the spill the secret at some point and that would mean having to kill them to keep them quiet if the MC would do the smart thing. So I think something Major like that needs to be a choice and not forced.
On your second point, I personally would actually like to see the MC travelling these other kingdoms rather than be forced to be a protector of this kingdom against them. Mostly because I don't like the current kingdom and want to burn it to the ground now, but also in doing so you have more of a unique story perspective. Instead of being the protector where the MC's viewpoint might be biased against them, exploring them and seeing and hearing from the people themselves as an independent would give both the MC and player the perspective of how these different races view themselves and open up the chance for more story telling through their unique lores or history as told by the actual people and not others. Plus imagine what kind of girls we could collect in these kingdoms too.
On your last point it comes back to the whole options thing and lack of them. If someone who is playing on a dark path or mostly dark route then yeah it would be a perfect opportunity to do so and more likely make sense considering how they have been playing, giving the player more freedom of control. In some games you know where there is a major plot branch and you get a warning before for the story. This could be it. You could either serve the kingdom or takeover or just get rid of it. With the show of force I never said it would be secret as everyone would know with the amount of people there. Which is why with making their leader submit before them you instill in all of them to tow the line or else. That they are only alive because the MC allows it. After that scene however and hearing how the guards talk though yeah I would go with the option of just killing all of them just to make sure.