I think you'll have to use a modified version of a content admin role:
You can restrict further that to a specif stream or even a specific app.
What is the normal/best practice for sharing apps that are created by one person and then worked on by another person?
Seems like a real pain to have to export and then import.
I made the person a QlikTeamAdmin using GSS package. They could see the Apps in the QMC and do anything to them except duplicate which was greyed out.