what is common between the active/passive setup and multi-instance setup is the way clients accesses using the IP and port, hence I was suggesting this as a possible workaround. Though the second node is up/running in multi-instance approach, the second node will be in read-only & clients cannot connect to that. It will become read-write only when the other node goes down, so a restart (or some action) is performed to make the passive become active and clients can connect. There is always a delay in-between (similar to a active/passive setup of broker). In many of the enterprise, there will be a MQ farm with real active/active setup in place.
Having said this, I understand this would be a workaround and not the real solution! The real solution is to get IS certified with MQ 8.0 which I believe is already requested by AXA via brainstorm. You may check with the respective Product managers or through account team to know exactly when this will be available.
webMethods and MQ series both are completely different technologies solving different use-cases. I am not sure why you thought, webMethods is ‘dictating’ the architecture of MQ. It is just that, webMethods has not been certified with MQ 8.0 as it was not tested so far.
Hope you can get more assistance with the respective product managers via brainstorm.
My 2 cents.