I can't really see how his metaphors relate to the superhumane at all, so i would have disagreed with the prompt. I guess it's not what you're after, but i would have said his metaphors are a figure for the two polar opposite categories of humankind. At one extreme end is all the characters denotative of avarice, zeal and gluttony. Where the "ebbs and flows" of society are plagued with corruption and amorality. The other end being Sir Thomas More, with his upright moral steadfastness, finding solace in the "thickets of the law", ie. solid ground. I probs would have chucked in a paragraph about the tainted cup, as it metaphorically denotes that of humankind's tendency to succumb to transient material lures. It can also be argued that the characters themselves are metaphors, representative of something or rather to do with Bolt's rendition of Sir Thomas More's life and 16th century Tudor England.