It’s true that each site will have its own data, but I just thought of a work-around… You could use the Sidebar.js feature to show the most recent posts across your account and embed them in a new “now” subdomain.
See the help page here: ℹ️ JavaScript include with Sidebar.js
You can actually paste this snippet of JavaScript directly into the settings text box with the “Custom home page” plug-in, so no custom theme is needed.
And make sure to add &count=5 at the end to just include the latest five posts.