A few of these can be solved with a comment.

"Need to see revision history for View-Only Google Docs" - Don't use a shared Google Doc as the agent of record. Email it to each other as an agreed contract.

"Can't find good replacement for expensive accounting/bookkeeper service" Have you tried literally anything else? You're paying $500/month for this solution, have considered just getting an accountant and emailing him spreadsheets?

"Monthly subscription for science fiction and fantasy books" "Subscribe to news without paying $30/month per website" - Existing solutions already exist and require a supply chain and distribution rights negotiation more than they do a developer to slap it into a webapp.