Just wondered if you managed to get anywhere with this at all?
If you could tap in directly in the Datawarehouse from the INsight Module it would be more straight forward.
I think your best call is to export the activity data out using the BulkAPI export functionality.
Exporting All Eloqua Activities Using the Bulk API: Flowchart, Best Practices, and Resources would be the best starting point.
Eloqua is only retaining 25 months of data in your Eloqua instance.
Once you have exported all the data out per activity, your best call is to have this data put into your datawarehouse or whatever database suitable.
you can also add up to 10 contacts field to your export definition. if you add your CRMContactID and CRMAccountID fields you are able to report on specific contacts or accounts.
If you add these fields you may notice that form activities not linked to contactIDs. The reason being the omission of the save data to contact record step (mapping only email address).
you can export the following activities using the BulkAPI. (clicking on the links you will be able to see export definition examples)
Hope this helps