Tracking any non-200 codes you would likely have to start looking at request logs, or maybe a LUA transform to catch any response with a non-200 and trigger some REST API to track the outage.
If you are only concerned with junction status as webseal sees it (personally that's the way I would go, much easier), you could considering using the junction status embedded application. It returns a JSON structure with the state of all junctions on the instance. Since it's an embedded app, it can be accessed from outside the instance, meaning away from the network where your instances (and config containers / primary cluster appliances) reside.
I would be curious what you end up doing. I've wanted to tackle a similar project for quite some time, but the priority keeps getting pushed.
#IBMChampion
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Matt Jenkins
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