Can you replicate Active Directory from a Corporate Intranet to an AWS VPC where there is an outbound-only link?
Yes, you just need a Read Only Domaine Controler (search for RODC) in the vpc and you'll be able to have a one way replication as the read only controler won't need to send datas back.

This bring limitation for clients in the vpc, as they won't be able to reach a writable DC they can't change passwords and you'll need a careful site architecture in your forest.