1 second system engineering work cycles: educated workflow setup for Docker-driven development
In some cases, depending on the actual configurations being targeted, it might be possible to try the effect of various changes live, using other automation tools, and only update the docker images (which acounts for a big chunk of that waiting time) after the bulk of the config changes are eliminated.

Stabilizing first the common/base docker image used across most/all of the candidate variants and sharing it would also help.