Hypothetically speaking, if you had a program that took Eyrie-standard .txt and converted it to HTML for you in one gulp -- possibly requiring spot checks and adjustments afterward if there was any unusual formatting, but no line-by-line proofreading -- how much of that process would be left?

I'm pretty sure that program could be written. I don't have time to do it myself, but I think other people have mentioned having already written approximations to it. (The hardest part, in my mind, would be the two-column end-titles-with-music pattern.)