There's already this for arXiv: https://www.arxiv-vanity.com/ https://www.arxiv-vanity.com/ Their job is a little bit easier because arXiv papers have the .tex

There's already this for arXiv: https://www.arxiv-vanity.com/ https://www.arxiv-vanity.com/ Their job is a little bit easier because arXiv papers have the .tex source available, so you can use one of the various tex2html variants, instead of having to extract the paper's contents from a rendered PDF.