Hey folks! Newbie here, and an artist to boot, so attempts not to get too codey in your answers will be appreciated. 
I’m currently trying to put together a nice template material for triplanar mapping. Basically, I want to make one material with all necessary settings exposed, so I can do material instances, and use it for loads of different things.
However, I’ve run into a problem: I cannot expose my textures as parameters, since they are feeding into a homemade material function that does not allow it. My question is this: How do I make my material function allow it? Can you look at my attached pictures and tell me what I’m doing wrong and how to fix it?
If you should notice something I can optimize in general, feel free to say that also. 
The error I am trying to squash, appearing when I convert the textures to parameters:
The full material as it stands now:
Inside the main material function:
Inside the secondary material function:
