API for ItemCode Imports

We are in the discovery phase of a vendor integration, previous vendor integrations have just been simple file transfers, no importing into SAGE, all exporting query results to FTP sites.  The next integration I want to explore if we can expand on the touch points, especially with items/products.  We are constantly adding new itemcodes from our vendors because we didn't want to add all the items they offer (could be over 1 million), so we added what we have previously sold, but everyday customers want a new item we haven't sold before.  My thought process is to create some kind of logic to pull the item data from the vendors API and create a "new" itemcode if it doesn't already exist in SAGE.  Question, I  know it is not recommended to add/edit records straight in SQL, but could this be an option, create the new item in the CI_Item table?  Or do we need to use VI in some way?  Anyone attempt something like this?