I'd be interested in hearing how this stacks up against simply running the tasks via shell scripts, because the time to install packages/do other tasks is orders of magnitude higher than the connection overhead. Things will always be slow when doing `serial: 1`, so I'd definitely recommend a canary setup where you run a play with a small serial batch followed by a play with no serial limitation - that'll speed things up considerably.

Finally, when using ControlPersist with pipelining mode in Ansible, it's as fast if not faster than zeromq or our own accelerated mode (which we will be deprecating at some future point when older SSH installs are not as common).