Is there a way to add a user to my DevCentre account so that they can view the reports, for example?
I contacted Microsoft support and got the following response:
Unfortunately, this is not an offered functionality at this time.
The same response referred me to Windows Dev Platform UserVioce site and I found the following request https://wpdev.uservoice.com/forums/110705-universal-windows-platform/suggestions/3820213-allow-multiple-microsoft-accounts-to-manage-a-dev marked as "WORKING ON IT".
In short, it is not supported now, but it will come one day.