The existing calendar functionality of 1 DU = 1 Calendar is not enough in case of the requirement to manage for each user the migration and an independent training calendar at the same time.
The training is planned typical at least 1 day in advance before the migration happens.
This also includes the selfservice for the user to receive an invitation for training and a seperate one for migration and also requires independent Email templates.
I actual used the workaround of duplicationg the user in migrationstudio with a quite similar DU name but this makes the handling unnecessary complex and doubles the costs of licences.
In summary the DU needs a 1:n relationship to calendars.