Not using migrated server in live after the migration

I would migrate from Windows Bitbucket server to a linux machine. I checked the following export-import plan https://confluence.atlassian.com/bitbucketserver/export-and-import-projects-and-repositories-957497834.html but its not migrating everything so its not good.

Meanwhile I checked the migration on the following link and my question is Migrate bitbucket server to server

Is it a working scenario to setup the migration to an external database but I will still use the old database?
My plan is to migrate the database from bitbucket1 to bitbucket2.
kepp the bitbucket1 working with the local database and when Im sure the bitbucket2 is up and running and I will do an second migration and switch the servers