On premise AD migration to AWS Managed Microsoft AD

Question

I have a small on premise AD environment comprising two Windows Server 2012 domain controllers. They run AD, DNS, DHCP, GP etc.

I want to migrate this to the AWS Managed Microsoft AD.

All the articles I have read suggest that the two AD environments need to be in different domains and you have to use a migration tool, and then re-add all your user PCs to this new domain.

Ideally I want to do the following:

1. Configure AWS Managed AD in the same domain as my on prem AD
2. Make the AWS AD servers part of the on prem domain, and promote them to domain controllers
3. All users start using the AWS AD servers
4. Demote and decom the old on prem AD servers

Is this possible, or am I being stupid?