@kawaii123456 An emperor could just as easily have any woman he wants, if they can't produce an heir they might as well get out of the way so he can devote his attention to the other women. Having a hundred heirs doesn't really mean much, they'll wittle their own numbers down with infighting over the throne. Or, assassination attempts from other parties will do it for them so some government officials can install a puppet on the throne or such. She kind of mentioned herself, all of those princes were already pretty much doomed in the original storyline here because the heroine basically just got rid of them on her power grabbing journey.
As for making the kid an arrogant young master... he'll die in the imperial palace if he doesn't look out for himself first and foremost. Not the best place to grow a conscience or have pity on those around you. This is some game of thrones shit, you can't trust anyone, least of all easily bribed servants. Anyone you actually care about can be used against you one way or another. You pretty much want them all to fear going against you in any way while also being the person who rewards "loyalty" the best. Even then, don't trust them as far as you can throw them with both arms tied behind your back. That's the kind of places these imperial palaces are in all the novels and comics.