Is it possible to create new heat resource types/plugins specific to my -cloud, and load them into my UCD-P. I’ll be using them to compose a blueprint in the BP Designer, and then to provision the stack by connecting to my cloud.

Once you have your new heat resources defined via your heat plugins, you can add them to your blueprint using the source editor. The Blueprint Designer does not currently support a plugin architecture so there is no way to provide DND capabilities for your new resources. Also, you might see validation errors with your heat resources in the designer, but I believe it interrogates the heat engine for the list of valid resources so this may not be an issue.

Also, this might be helpful information about writing heat plugins: https://wiki.openstack.org/wiki/Heat/Plugins. 

Thanks both--I was able to solve my problem.