I think it would be very useful to have the DLL project included in the base SDK. In addition to letting us tweak the Unity integration, that DLL could be very useful for binding to other languages such as Java and C# outside of Unity, since it has C style calling conventions and only needs a header in the application code.
Some developers will also just want to keep the sdk separate from their game code for dependency management or patching reasons, and having a DLL build option will be more attractive to them.
