It would be really nice if we could indicate the unit of the literal we provide for the "plain" mapping of quantity values. The plain mapping should always be a single resources or literal. So the unit has to be either encoded into the string, or into the literal's type.

I think something like "12.7"^^wdu:Q828224 would be a nice representation. But we would have to somehow indicate that wdu:Q828224 is a subtype of xsd:decimal. The declaration of that relationship needs to be included in the RDF output, and we would have to make sure that consumers, in particular WDQS/BlazeGraph, will understand hand treat the "12.7" as a decimal value, not a plain string.