Could snapd/snapcraft maybe support an android/ios/windows like permission manager where the application could also interactively request permissions/interfaces to be granted either temporarilly or pernamently. I am aware you can connect interfaces and I can see some parallels which mostly seem to cater to pernament granting of permissions.
Sometimes applications, just need be able do an infrequent or one-off task could normally invole an restricted interface connection. I think it would benefit system security, if application don’t always have to be designed to preemptively aquire the broadest set of priviledges, but also have an option to aquire it on-demand when actually needed.
A different use-case could be when you have a plugin system, plugins could require some kind of interfaces to function, plugin’s often run in the address space of their host therefor the the host should have the sum of interfaces of all plugins so it would be nice for example if you have a bluetooth plugin for an application, that maybe bluetooth permissions could be granted to plugin-snap and automatically used or requested on demand by the consumer of the plugin.