Is there a way to determine if a model is needed or not...

I am working on a new mod and I have a lot of models in the models folder and I don't think all of them are needed. I was wondering how you know which models are critical to the mod and which ones can be removed so that I can have as small of file as possible?

It's not as easy as if the model was used or not because some models that I tried to remove caused the game to crash and they were not even in use. But some other files that I removed worked fine.

So, is there a way to know without a lot of trial and error? (That could take a very long time) Thanks!