Are you keeping an eye on how fast Rhino inside Revit is developing? It is maturing really, really well. When I first saw the Grasshopper Archicad connection it was long before the Rhino Inside Revit project started. Unfortunately, Archicad GH development is very slow and is way less powerful than RiR.
I'm Rhino first user and if I want to leverage all the good things Rhino is allowing me to do I can't choose Archicad... I must stay with Revit.
Integrating another program into your own would be a lot of work, and if a large proportion of your user base cannot even use it due to OS restrictions, and and even larger proportion would not use it, why spend the resources on it...
AC18-23 AUS 7000 Self-taught, bend it till it breaks. Win10 | E5620 x 2 | 24GB | K2200