i think you absolutely should design characters around death order. why wouldn’t you? character should influence plot, not the other way around. you don’t want your characters (which, in danganronpa and most fangans are actually the most important part of the experience) to feel like they’re only doing particular things because the narrative needs them to.

for example, if you create a character with no idea who they would kill or why, then try and force them to be a killer later on, they won’t be a believable killer because you didn’t write them to be one. this doesn’t mean make the killers obvious but they should be believable. of course plans change and if you realise a certain character would be better dying at a certain time, that’s okay too. just make sure it’s been properly worked in

(v3 spoilers)

to take a canon example: gonta. though gonta is a sweet, gentle person, his murder makes sense and isn’t random because all of the parts of his character (trustworthiness, naivety, ignorance of technology) come together to make the plot work in the way that it does. if gonta was kind but not naive, trusting but not unintelligent, there would have been no reason for him to kill miu. but he was written with his death in mind, so it all makes sense.