This was shipped in the first release of Bulk Import in Q2 2018. Bulk Import is available to the majority of our hosted customers.
You can pull the real GUID/Lookup ID by mapping an alternate ID in an import selection. It's how i get around this, but would be super nice to have this feature!
Alternate IDs are a key way to connect CRM to other systems. Should be able to easily import them.
You won't be notified about changes to this idea.