This is a great project! Sadly SE has a focus on ePub and similar formats. These are impossible from a typographical standpoint. Text in ePub reader apps always comes out with a ragged right or impossible word breaks.

Latex with the microtype package is the only solution that does text justification on the level of a human professional. Can’t SE convert to that and provide PDF for common screen sizes?

It would be so easy if only Project Gutenberg had a standardized master source format. So conversion tools can be built around that. But all efforts in that direction were killed of by trolls in the community.