Is it possible to create a RHEL 6 repo on a RHEL 7 server
The repos for RHEL 6 are not available for RHEL 7 because there would be a carnival of package conflicts, dependency hells on earth, and utter chaos.
Can you imagine
yum trying to install RHEL 6 packages or just packages that aren't compatible with what's available in RHEL 7 because the former is deprecated?
subscription manager doesn't allow what you're trying to do for this very reason.