I’ve already done most of these in my Symfony projects (using Phing instead of make because of consistency, but that bring about another set of problems) so all of these sound great.
What I feel should be addressed is somehow providing an equivalent of a env-based parameters.yaml.dist file. The file provides a way to ship some easy defaults (very useful for Docker based environments) or even only a way to enumerate all the required variables, with samples how they should/might look. Created an issue here: https://github.com/Incenteev/ParameterHandler/issues/108
Looking forward to Symfony 4.