I don't know if this is on your todo list but I thought It would be good to throw it in here.
The tabs (and maybe all the elements) in the admin dashboard could be generated in a more abstract form.
I mean, the dashboard should be just a list of placeholders that can be filled in by the rest of the modules.
Right now the Magento\Backend\Block\Dashboard\Grids::_prepareLayout contains 4 hardcoded tabs that should be moved in the correct module.
For example Bestsellers and Most Viewed Products could be part of the reports module, New Customers of course in the customer module and so on.
Also a way to add custom tabs could be nice. I know about interceptors, but I'm not exactly sure I can intercept a protected method.