it's still easier to manage docker containers if they're 50 MB instead of 300MB and if the rest of the fleet is being managed via docker-(whichever) then there's something to be said about consistency. managing everything through one interface is easier than remembering all the special cases. but to each their own.
I don't even like docker, but it still doesn't sound that terrible to me. It's an option. Use docker or use the single binary, but presumably if you like docker and have it set up for other things, you'll just use that rather than rolling your own startup scripts etc.
I do something a bit similar for my own project - it's a single binary REST server, but I still package it up with dpkg-deb and deploy that to a private apt repo so I can update it easily on the servers with "apt-get update && apt-get install blah" and that fits nicely with my existing processes and I can just add the repo and dependency to my cloud-init setup. If I used docker, I'm sure I'd find his docker image the easiest path to getting it installed and updated.
Consistency is key. it's easier if you're using docker to run all the things, then docker ps shows all the things running, instead of having to check docker, and then also check this other thing over here that's different
And what's good about a single binary if you're going to recommend Docker?