We typically go an extra mile in the modeling process to minimize later needs to change existing links. When we model a specific source table, we try to identify all relationships, and no matter if the tables they point to are part of the current scope, we identify the business keys for them. Now we can create the full link, that might point to hubs that are not created yet, but we don't need to touch the link later on. Of course, if you identify additional relationships later, that you weren't aware of before, you still need to touch what you have.