subscribe a device to multiple groups
Allow a device to be a member of multiple groups to inherit additional configuration profiles from each group
Agreed. This is currently possible with Apple Profile Manager and many other MDMs.
One use-case: if we have 5 different device roles requiring different settings and apps and we also have 10 different locations requiring some different settings, we will need 50 device groups - one for each role/location combination, rather than just 15 device groups when we can assign a device to both.