Thanks for your feedback! Just a note to let you know that we’re building your suggestion now.
Corporate lifecycle is a real and constant pressure in business, often resulting in a need to rename the Office 365 Tenant. To that end we are working on the solution to change the SharePoint domain URL (contoso.sharepoint.com renamed to fabrikam.sharepoint.com). This capability will also then enable the renaming of an individual site collection (contoso.sharepoint.com/sites/abc to contoso.sharepoint.com/sites/xyz).
While we don’t have an estimated delivery date to share at this time, we’ll update your suggestion with details as they become available.
Bill Baer MSFT