Hey Doug, thanks for reaching out!
At this time there isn't a way to connect to the underlying data of your Online site through Tableau Desktop to create vizzes. However, it may be possible to accomplish items 1 and 2 using the Tableau REST API - I'm thinking something with the Get Users In Group, Get Users On Site, Query Groups, Query Workbook Permissions, etc. If you're interested in this solution I would recommend checking out our Rest API Samples page on Github and also engaging our Developer Community forum for any questions.
This is a great idea so I would encourage you to submit it to our Ideas forum for other members to vote and discuss. Posting there will also allow our development team to gauge the demand for each enhancement.
Thanks for the input. I will submit as an idea.