Thanks for the feedback, happy to try and address each of your comments. :)
We're always looking at ways to make the reader as user accessible and customizable as possible, so the full customization has really helped people set things exactly the way they want. Additional font options are certainly an option in the future.
The need for an account is driven by the primary purpose of the platform which is to make your digital library accessible on all your devices, and sync any progress or highlights across them so you are always in the same place wherever you read. However, we have definitely heard that some users just want to read locally on a single device with no concern for syncing, so in the future we'll be making an enhancement to allow the mobile apps to simply open books without an account.
We're actually looking at a multitude of ways to best handle endnotes/footnotes, so I'm glad to hear it's a big issue for you since that likely means it'll be a big help for not just you but any others who feel similarly. :) We have an open beta for both Android and iOS, so you're welcome to get in on early access features like that when we start testing that kind of new functionality.
We haven't explored an option like a URL to go get books, but we're also not averse to future improvements like what you're describing. The main reason we didn't do anything like that from the start is the desire to create the easiest interface and experience possible for readers who use the platform, meaning we allow uploading books for those who have their own libraries of eBooks, but we also provide a store for purchasing directly from publishers and a Library section where free books are available without ever having to leave and go browse an entirely different site and interface.
As for the "via the web first" part of the iOS app's store description, I'm actually going to have to take a look at that. You can absolutely upload multiple formats directly from iOS, including CBR, by browsing your iCloud Files, so it's most likely a bullet point we need to refresh after improvements were made to the app.
We use our own sync that we built which is why the BookFusion account is what drives that ability to have them connected; even if you sign in with Apple or Facebook or Twitter instead of a newly created BookFusion account, you'll still have a profile that allows your progress and books to be carried across any device you want to use. We are looking into 3rd party integrations that many readers have asked for like Readwise where they'd like to sync or export highlights to in the future, but that's coming next year.
Appreciate your response and happy to continue the conversation. :)