>You are not listening. You don't need round trips.
Ok, so you've already proposed to me that my server not only needs to know how to load all the data, it also has to have an HTML renderer baked in, AND in your haste to say my SPA doesn't have any advantages, you've already forced your server to execute a layout algorithm on N graphs of unknown complexity, on your own machine & dime instead of your client's, just in order to accomplish what my SPA got for free: instantly rendering the next content when the user clicked.
The fact that you can come up with a list of things orthogonally related to serving web content that aren't solved any more gracefully with server-side rendering than an SPA - SEO, semantic content, accessibility - it's just silly. Same with this idea that you're going to pre-render the HTML into an ingenious layout where the user makes a series of actions that uncover nested HTML and don't require round-trips. It's as if you're ignoring that a primary benefit of SPAs is you can hide data loading really easily with prefetching JSON blobs and writing JS to navigate the tree. It's literally the language for the task.
It's exactly why I've not been shy to say this: anti-JS anti-SPA users get so bent out of shape that SPAs build nice UIs that they throw the baby out with the bathwater.