The problem with render engines is you must consider what type of program poser is. It is a content manipulation program. It is essentially designed to bring in external content, set up a scene or animation and render it. Users must be able to bring in content designed for poser and be able to easily render it. I've tried using Reality for poser. Every scene I had to modify lights and materials. Now if this was the same for these other render engines can you imagine the nightmares for content developers as they get constant requests for support asking how to use content x with renderer y. Also this brings us back to the problem of poser , and it's content, being tied to developments beyond their control. I'm not saying this would ever happen, but suppose poser didn't create superfly but instead had a bridge to cycles, and then the cycles development team decided to streamline it and get rid half the nodes they considered obsolete? Suddenly a large chunk of your pbr content would no longer work. IMHO poser must have it's own renderers, which users and content creators can rely on for continuity going forward.