Seems strange that you don't have C++ SDK as well. Unity3D is great, but what if someone wants to add support to an existing 3D modeling application? Even if you're primarily targeting indie game developers, what if I my engine of choice is UDK instead of Unity3D?

Depending on how you implement your Unity integration it probably wouldn't be very hard to add support for other code bases, but if you want a lot of developers making applications for Meta it seems like you'd have more options available.