I created something very similar but to display raindrop links into the remarkable and sync highlights back into raindrop. I also added a GenAI powered paper summary filter as a preface to the papers it send to the remarkable which is working quite well.

As you mentioned Remarkable file format is a PITA to extract highlights, one thing that helped a lot was to add an OCR fix phase that uses Gemini flash model to fix common OCR errors and to merge single highlights that are across pages.

Adding that I've worked on a CLI install flow which walks you through setting up Zotero, reMarkable, and key optional features as switfly as possible.

It leaves aside power user features (e.g. emails, GitHub Actions to sync when laptop is asleep, etc.), which are listed here: https://distillate.dev/power-users.html