We have some sites where the monitoring is being performed by a robot attached to a hub rather than the hub itself. in this scenario the hub doesnt have access to the target devices but the robot does. we can run the snmpcollector on the robot and use that to monitoring those devices. the robot doesnt have a direct connection to the primary hub but any data including probe discovery data gets passed onto the hub. from what i remember about the discovery_agent and usm is that the UMPs and discovery_server need direct connectivity or through tunnels to the discovery agents.
We propose that the snmpcollector, when performing a discovery on a target device, collects the information it collects now and also collects the same information as would be collected by the discovery agent. this would mean that the restriction wouldn't apply. it would also help in the case of discovery not being used in the environment or MSP if access is restricted down.