Assign Template In HTML File

The ability to assign templates on page. Possibly a special line in the head.
Then one would be able to assign templates to pages uploaded with FTP, in the HTML instead of assigning them after upload.

For example 11ty uses something like this. They have a head section on pages delimited by three “—”

i.e.
---
layout: mainlayout.html...
				

• Pages and Templates