As a pythonista, I am a huge fan of the plumbum library as a replacement for bash. It makes it very straightforward to run a sequence of *nix commands, but you get all the simplicity and power of the python language in terms of loops and functions and so forth. These days, I do all my server management and deployment scripts with python/plumbum.

And while simple is great, the necessary features not included in OP's scripts is that I want to spin up the new instance in parallel, verify it is running correctly, and then switch nginx or the load balancer to point to the new server. You are less prone to break production and you get zero downtime deploys.