The essays have some hyperlinks in them, how could audio be as 'interactive' as that already is? It seems you mean something other than 'interactive'.
Anyway, I don't see what's "just" about reading someone's essays - it's my favourite thing in life. People like Hazlitt, Stevenson, Chesterton, Santayana, Russell, Emerson - and, yes, pg - I think he's a great essayist, my favourite from recent decades.
I've never been into audiobooks. I tried a few years ago - but all bad, terrible pronunciation of names, usually inappropriate US accent, etc. I hear there are good ones, although that was just novels. Also, when reading, I like being able to stop, think about what I read. (Not like a read-aloud story where the storyteller's pace is usually fine) Being able to stop at the end of a sentence, and repeat it, or repeat paragraph, or page, would be good.
I used to have tapes with hours of famous poets reading their own poetry - Yeats, Eliot, Plath etc - they were so awesome. Then when you read their other stuff, you can hear it in their voice. It's like that e.g. reading Rorty after watching a lot of video of him speaking, I can't imagine not having heard/seen him.
IIRC he is active on Twitter. Also, try sending an email.
(Perhaps sending him a one minute demo of one paragraph may convince him that your product is good (, or he may get a lawyer and send a CD letter).)
(If your product is good, this is a scary word.)
(Note: I read the emails from my friends with their voice. The difficult part for an automated version are the intonation of each sentence, the pauses, and which parts to stress.)