Fair point but the reason I added was to for completeness and because CloudFormationTemplate.mappings is a JSONableDict to which you can only add() other JSONableDicts, not a straight up dict.

Your argument that Mappings are not useful in the context where you're building a template with Python/py-plates is valid - one does far better to use PYthon constructs and the options mechanism that py-plates provides. However one might be generating templates for use by people without py-plates and who will be using the web interface to launch stacks and creating templates for this purpose benefits from Mappings.