Strategy pattern with blueprint interface

Hallo guy’s,

I use a blueprint script, that computes the sun and moon position an keeps track of time and things like that (it is called DayNightSystem).
Now i want to use multiple sky spheres with this script, without changing all variable types.
To do so i want to use a strategy pattern with a blueprint interface as common parent.
I want to use this interface inside the DayNightSystem, as a replacement for the sky sphere variable, so i can change the different sky spheres.
Like you would do it Java or standard c++.

But it dose not work since there is no way to create a blueprint interface reference variable inside the DayNightSystem.

How can i achieve a behavior like this ?