I understand your enthusiasm for a SU solution — Grasshopper is an amazing, mature tool that has virtually infinite parametric modelling capability.
But I think you have to be realistic as to the potential addressable market for such a tool in the SU context. The user base for Rhino is heavily weighted towards industrial design professionals - for whom the need of parametric modelling is much more widespread, and incorporated into existing workflows.
The amount of work involved in developing and maintaining a SU/Grasshopper bridge extension versus the percentage of SU users for whom it holds appeal — and would be therefore willing to pay for it — wouldn’t likely pay off for the developers.
I haven’t seen a massive amount of interest in Viz from the broader SU Pro user base and I suspect that it therefore hasn’t sold in large numbers — which I would submit, suggests there isn’t a significant addressable market there.
This is the development constraint, and not the technical challenge: I have no doubt that any one of the genius extension developers on your list would be up to the task. But I really can’t see it being worth their time - especially in light of the fact that their is already a well-realized tool available in this space.
… and apologies for raining on your parade