You may be right on that; however, given that there seems to be a very prominent focus on the puppet master role, it could very well be possible that no alignment harbors a killing role, whether vigilante or mafia kill. Come to think of it, I may have misread Jamie's post:
Well it's all speculation, but even with a unique flavor I'd expect the mafia to still retain a base level faction kill.
The randomized scenario potentially indicates at the mafia also receiving a chance at the reins of puppet master. If the mafia had their nightly kill function in conjunction with the former skill, the balance of the game may seem unbalanced.
This also seems very possible and obviously this option is the least favorable.