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Option C) doesn't work for all applications/tooling, like defining custom API connectors in the 365 PowerPlatform. In those cases the same static structure for all call responses on a specific endpoint is expected/not only IBP but also required.
As on WMDA side (propably) all messages are stored in one queue anyhow (check with Mark) options A-C) will only effect the exposure of the messages to the registries and not the internal workings on WMDA side.
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