Uploading Purchased Data for Leads

I am cleaning up an implementation of Salesforce that is a few years old (we're a startup).  In that time our process has evolved and our reporting/data needs have evolved accordingly.  Below is the scenario:

• We regularly purchase data for our call bank.  We internally need to associate these leads to other data before it's uploaded to Salesforce.
  • This data includes data from standard and custom objects that pre-exist in our SF instance: Account Object Data, Contact Object Data, and Building Object Data (this is a custom object for us)
  • Despite this, The current process (for all previoius data purchases) is to upload data to the Lead Object where we duplicated ALL the fields from Account, Contact, and Building objects as custom fields (again, on the Lead Object)
  • This caused a number of problematic things at a data and therefore reporting level (really fun times).
• We're preparing to upload our newest data purchase for the sales team (the first in my tenure here).  To me it makes sense to :
  • Upload Building Data to the Building Object
  • Account Data to the Account Object
  • Contact data to the Contact Object. 
  • (In the order it makes sense to upload them in the ways that they relate to one another).
• And then finally to upload a Leads file that relates all of the information together (rather than duplicating all the fields and data on the Lead Object)

My question is...Does anyone else out there have experience with creating Leads from purchased data?  Does this sound like a reasonable thing to do?  Does anyone have any best practices to recommend?