Hi Detecjack!
Sure! As you said “Weapon” is the murder weapon and “Motive” is the drive that drives him to kill. It can also be described in the clue in a very material way, such as “a bag full of money” or “the inheritance papers,” or even in a much more emotional way, such as “a secret lover.”
“Accomplice” is exactly what you described, and just as you emphasized, it can be voluntary or involuntary! Furthermore, its power is that of creating an NPC.
By “opportunity,” we literally mean “the occasion” that makes the murderer a Killer. A moment in which he can act to commit the crime. Examples include “The Night in the Room,” “On the Balcony Smoking,” or “During Dinner.” They are primarily “temporal” clues.
The “clues” are essentially “ideas” and suggestions for creating the murder story, a bit like “mandatory stages” in the narrative, and our idea was that each clue created a “narrative object.” The weapon supported the descriptions, the Motive supported the relationships, the accomplice generated NPCs, and opportunity suggest the timing :)