Seamlessly switch between CloudFront distributions using Route 53?

My customer wants ultimately to migrate multiple CloudFront Distributions from one AWS Account to another but realize it’s not quite possible.

Right now their CloudFront Distribution is configured this way:

• CNAME of the CloudFront Distribution is the same as a production customer-facing FQDN (e.g.: download-office.customer.com)
• in Route53 customer-facing FQDN is pointed to CloudFront Distribution FQDN using CNAME record (e.g.: download-office.customer.com CNAME d11ipsxxxxxxx.cloudfront.net)

What they want to do is to introduce an intermediate FQDN and place it in between the customer-facing FQDN and CloudFront Distribution FQDN using Route53 Alias Records. So the configuration would look like:

• CNAME of the CloudFront Distribution is the same as a intermediate FQDN (e.g.: balancer-download-office.customer.com)
• in Route53 intermediate FQDN is pointed to CloudFront Distribution FQDN using ALIAS record (e.g.: balancer-download-office.customer.com ALIAS d11ipsxxxxxxx.cloudfront.net)
• in Route53 customer-facing FQDN is pointed to intermediate FQDN using ALIAS record (e.g.: download-office.customer.com ALIAS balancer-download-office.customer.com)

It's working in their QA environment but they would like feedback on any issues. However, they are finding from support engineers that the only way to swap a CloudFront distribution without downtime is specifically through a support case.

The question is: what is the best way for my customer to seamlessly switch between CloudFront distributions, and ultimately move to a CloudFront distribution in another account without downtime?