Yes, you can upload OSM's to BCL; it is done through a component. A component has an XML file with attributes, and then optionally has one or more external files which could be OSM, IDF, EPW, etc. Components are the original use case for BCL that pre-dates measures.
Unless you are in a hurry I would suggest you wait until July when a re-factored BCL goes up. This new BCL for both measures and components will get content form public GitHub repositories.
Here is one of the measure repositories. The measures are under lib/measures
https://github.com/NREL/openstudio-co...
And here is an example of what a component repository would look like. Components are under lib/components
.
https://github.com/BuildingComponentL...
We will work on updating scripts to make components. This can even be done through a measure. Here is API documentation for component and component data
https://openstudio-sdk-documentation.... https://openstudio-sdk-documentation....
If you pick an object with children or resources like a construction, it should grab the materials into the OSM file.
One last comment on components. While you can make a component out of any OpenStudio object, or anything, specific interfaces may only expose specific types in their GUI. In the case of the OpenStudio application constructions, materials, and some HVAC objects are supported. A work around to expose any component is to access and download it via a measure. This strategy needs more work to better support re-using of downloaded components on parametric analysis so it only downloads it once for each analysis.