I didn't want to use something like tmuxinator for annoyance at one more dependancy on random machines, and write bash scripts to make custom sessions as necessary.

This appears to way easier to do tricky things super fast than the wildly obscure language needed to write a small script, and its literally just a bash script itself, meaning it's as portable as almost anything. I love it.

Thank you OP! (Assuming you are the author of the tool given usernames here and github)

This reminds me of ClusterSSH, although I think I would rather use ClusterSSH since it will tile a bunch of xterms across all of my monitors and let me point to click to address just one if needed. But, still, this is pretty cool.

Even if you manually manage hundreds of machines over ssh, I am still not sure how useful this can be.

For one, you still need to manually inspect each window and issue further commands.

setw synchronize-panes would help perhaps?