In the current state you can't handle nodeLostService alarms different. Every nodeLostService alarm has the severity like it's defined in the event configuration. And that is MINOR.

That's totally nonsense.

In the field you always have services on your interfaces which are more or less important. So a MINOR alarm is not always correct. It should be possible to define the severity service on a node/interface separately.

Also you can't use BSM for this scenario because you will get the normal nodeLostService alarm with MINOR and the BSM alarm with a self defined severity which brings more confusion. Also BSM events are not very informative. eg.: https://issues.opennms.org/browse/NMS-9352