If you add the application to both server groups the domain will redeploy it in parallel.
I suppose that you have to add the app with two different names and deploy one first.
But I think there will be a small gap as running requests might be interrupted during deploy or fail as the node where the request is routed from the apache in front might in the middle of re-deploy.
thanks for your response
I thought the same actually and deployed two applications with different names (same web context root) to two server groups and this seems to work as the re-deploy is serial by manual process. I would not personally use this in a production system as I feel it would cause confusion, if there is no better solution I would prefer to have two domains.
I think that is a individual desicion I would prefer the single point of configuration but that are my two cents.
What I often saw is that such processes are scripted or there is a document which describe each single step and nobody think about it (as long as it works )