From Exchange on premise to Office 365 - will this work

I would like a confirmation if this is a valid approach to this.

1. Under the client and before validating the actual domain we assign liscenses to 5 users on portal.office.com
   
2. them a valid address Bill.saunders@onmicrosoft.com and valid Exchange liscense on office 365.
   

3)From on premise exchange management console we export bill.saunders account to a pst file.

4)Launch Outlook on a random computer and create a new account for bill.saunders@onmicrsoft.com and import the 20 GB pst file to that outlook and 2 days verify that it has been synced to MSFT

By checking that all the emails are there using portal.office.com. All the emails are there and we are all happy.

5)Then 4 days later we add the abc-compay.com domain to Office 365. And set bill to use the Bill.saunders@abc-company.com as his primary email address. (and change mx records)

6)...