Yeah, I'd rather use a Trigger and/or an activation roll rather than futz around with AI for Coinspinner.
Meanwhile I found that Surbrook has a writeup for Stormbringer already. It's missing some features that I would have included, like the rare interdimensional teleport and the bloodlust it ignites in its wielder, and I'd make the soul transfer into an NND, but otherwise it's a solid writeup.