MERCI can extend any content type into a list of unique reservable items (like studios) or buckets of interchangeable items (like DV cameras). We followed the approach used by Organic Groups, Feed API, and Scheduler and added MERCI's configuration to the Edit tab of those content types.
The Node Reference URL Widget module adds a new widget to the Node Reference field type. It auto-populates a node reference field with a value from the URL, and does not allow this value to be changed once set. It can automatically provide a link on the referencing node types, that will contain the proper URL to prepopulate the field.