It would be good to have a list of YAML capabilities to support natively. I can see binary data being useful in certain context.
Well, if you can get a list of core features that needs to be kept, then that can be a start (And maybe we can forward that to either YAML or diet-YAML team.
A good yardstick could perhaps be if it can convert from/to json/json5 at the least (if I remember json is not very large of a specification).
Alternative proposed name for this stripped down YAML:
cYAML - Core YAML - C YAML : Small fast minimally specced YAML with fast C reference parser. (I think at minimum, you should be able to convert between JSON and YAML)