The British can sound incredibly removed, austere and cold. It was good to be able to use that. I've got a great voice. I get other people to do my answering machine message. Part of the reason seasoned actors like Driver were chosen for Princess Mononoke is the sophistication of the material.
Motives are difficult to discern.
It's a complex film. There is a lot of subtext and a lot of stuff going on under the surface. For example, Lady Eboshi has no qualms about potentially ruining the balance of nature. At the same time, she gives hope and opportunity to outcasts like prostitutes and lepers by recruiting them to work in her village. Flawed characters are always more interesting than the aesthetically perfect ones.