General :: Set Default Permissions For Files Moved Or Copied To A Directory?

How to set the default file permissions on ALL newly created files in linux - but differs in important ways:

I want all files created in (or copied to or moved to) a certain directory to inherit a set of default permissions that is different from the system default.

Rationale: The directory in question is the "intake hopper" for an application. Users in a group place files in the directory, and the app (running under another user id in the same group) takes them and processes them. The problem is that the owner of each file placed in the directory is the user that placed it there, and the permissions are defaulting to "rw-r--r--"; I want to change that to "rw-rw----". The app doing the intake can't do that explicitly, because the user id the app is running under doesn't own the file in question, and the default permissions don't allow the app to chmod on the file! Obviously, the user could do a chmod after putting the file there - but I want to keep the "drop" by the user as simple as possible. (These folks are not linux-literate, they just drag and drop the files from their windows desktop to a (Samba) network share - i.e. they don't even know they are interacting with a linux system.)

umask seems too powerful: I don't want to set default permissions for every file created anywhere by these users - just those created in (or placed in) this directory.