content type – Hot do I make fields for documents but not the doc set they reside in?

I need to be able to create document sets where each document with the doc set has a required field, without requiring that that field be required when the doc set is created.

When I click on “+ New” in our document library, the only option is to create a new document set. This is how we want it, but at the Doc Set level, we only care about a location and borrower name as seen in the following image:
Required Fields for Document Set

Once we click save, however we need to have a required column (called “Borrower Doc Type”) that ensures users designate what type of borrower document they’re uploading to the document set. This is a Choice column that will be different for each document with in the doc set. We have tried the following:

  • adding the custom “Borrower Doc Type” column to the Doc Set as required – This makes it so that the user is prompted to add the “Borrower Doc Type” when the doc set is created, but that is wrong because there is no single Doc Type that applies to the entire Document Set. We just need to know the document type of the files added to the doc set.
  • adding the custom “Borrower Doc Type” column to the document library – This ensures that the user doesn’t have to enter the Borrower Doc Type when the document set is created, but it does not make the column required for documents uploaded to the document set.

We’re using SharePoint Online via Office365. I feel like I’m running around in circles trying to figure this out, but I’m positive it should be a simple solution.