My understanding is the co-processor handles specific tasks, such as the camera or video decoding. The iMacPro uses it for system authentication at startup as well, but reports are that has had many issues at release and it CAN be disabled for that task. If those are the only type of things the co-processor is handling in MacPro7,1 then fine... but if it's looking for specially blessed SSD, RAM modules, or PCIe cards (even in an enclosure) connected to the machine then they can find some other buyers - the majority of people I work with will NOT be interested.
A pro machine of this caliber needs to be able to access cards like NVIDIA GPUs, RED ROCKET-X style accelerators, and MANY others in some capacity. The majority on this forum want that to be internal, but even if accepting that may be external, there is no reason that access should be blocked. Anything preventing that from legitimately happening with proper software and drivers being provided by the manufacturer would not be acceptable for a pro machine.