Enable Permissive Browser File Handling
I think it would be useful if one could enable "Permissive Browser File Handling" per SubSite instead of doing it for entire Site Collections.
Or if one could refine the granularity even further: "Per Folder" would be even better! - so one could run little HTML projects from within a Document Library, without compromising the security of any other collection, site or folder.
Vinod Kumar commented
Our organization several thousand users are impacted. They are unable to view several thousand HTML pages that have been generated from applications that have references to other HTML pages. As suggested by Adam the permission should be at the SubSite level. In a multi-tenet environment this is a very restrictive condition.