In OIL, we test various SDNs on the same hardware. We use eth1 on our nodes for a data network for openstack. Some SDNs require that interfaces on that network be unconfigured (neutron-gateway with openvswitch, for example), and some require that it be configured with an IP address - auto assign is fine (nova compute for calico, for example).
To accommodate this, we have to carry code in OIL that talks to the MAAS api to either configure eth1 for auto-assign, or leave it unconfigured, depending on which service/bundle we're deploying to a node.
juju/charms should have some way of modeling this and handling talking to the MAAS API to do this configuration, so that we (and everyone else deploying services with different requirements along these lines) don't have to carry custom external code to handle it.
I thinks this very needed and would also open additional possibilities for doing config validations. i.e catching binding conflicts early when services are collocated.
Bug 1659376 describes a failure which could be also be addressed by this if say we could also integrate state information into bindings.