Pretty sure there is no way to have a package-specific #define, so you have to have your own project-specified #define set.
Keep in mind you don't need it if you use reflection instead. Just look at how I handled runtime code execution or look at TNet.TypeExtensions. You can use Invoke to call a method by its name same way Unity can do it with its MonoBehaviours, except this is much faster and works with everything.
