Cassie is a hero and I love her dearly, but Lord no. The Ring would play to her pride and family-related anxieties. She'd go out like Boromir.

Garyn is stout-hearted and stubborn enough that he'd get far. But he absolutely would not be able to get as close as Frodo did - he has actual ambitions and the Ring would get him that way.

Ecco, on the other hand, would be good to go if Amon Amarth was an undersea volcano. Why didn't the Fellowship just ride dolphins to Mordor?