Virtual DocType? Or how to best relate third-party data to another DocType?

I’m building an app that integrates the Dropbox Sign API (formerly HelloSign) to send documents for signature. Note, I am NOT talking about the standard Dropbox API that is used for file storage etc.

When the signature request is sent via API, Dropbox returns a signature_request_id which can be used to check the status of the signature request via their API.

I do have a DocType called Signature Requests, which is used to create a record of each request sent (in case the user cancels their Dropbox subscription), but I only use it to store basic data about the signature request, not all of the data that Dropbox stores.

So, I want a good way to display the data from Dropbox without having to store all of that data in the database. I think that Virtual DocTypes are the feature I am looking for, but thats not something I have built with before.

Has anybody done something similar?