I have been watching this post for some time in hope that someone will create an answer. I have not been able to find a definitive answer to this question if Commerce Profiles Imports can't be liked to users it is not usable!
We have found a workaround for this but it is far from ideal.
This requires modules:
Step 1) User Import
We have alphanumeric unique account codes for customers that are used user name. This is straight forward.
Step 2) Billing and Delivery profile imports
Our import file has two identical account code fields AccountCode1 AccountCode2.
Step 3) AccountCode1 maps to the GUID so we can update or delete the profiles. (Important note: if you set the import to update existing profiles and the profile is already assigned to an order it will create a new profile on every import that will quickly bloat your database.)
Step 4) AccountCode2 maps to field to a Profile Entity Reference field with target type User. The import reference is then "Customer code Ref: Entity ID of target user". The feeds tamper "Convert string into entity ID" is used to find the entity id of the user. When the import runs the account code is then imported and we get the entity ID stored in our Entity reference field.
Step 5) On import a rule then fires "Before saving an item imported via Customer: Billing Profile" that copies the value from our Entity reference field to the commerce-customer-profile:uid.
The problem we have with this is that it works 90% of the time but we often have two digit account codes and these get confused during the auto look up therefore account ABC will often add the profile to account BC.
Has anyone had any success importing the account codes straight into the UID field using the "Cast to integer" tamper?