Make the Nightmare Werepig and Frostjaw bosses able to be killed. As an example, the Seal from Sealnado is another mob that can be fought and then either spared or killed if the player chooses to do so and it should be the same here. If the player does choose to kill them, their could be an indication that maybe the player shouldn't, such as when hitting them in their defeated state they ask to be sparred and have an animation where they cover their heads, on top of making them take several hits, so you don't accidently one tap them and so that it is properly communicated to the player that *maybe* you shouldn't do this, but the option is available.
I am asking this for consistency, if I fight something I should at the very least, bare minimum, have the option to kill it. Lest we forgot this is a Sandbox/survival game after all.
the Drops for each can be
6 meat, 4 Pig skin for Nightmare Werepig
8 Fish meat for Frostjaw
including their regular drops of course.
I understand Klei possibly has future plans for these mobs in question but that does not mean they cant add this nor does it intrude on these future plans as this is completely optional if the player chooses to kill them or not.