Calling the illegal pitch

[TexBlue]

I don't think you can call an IP until the pitch starts (ie the separation of hands or the start of the normal pitching motion.) As you said, a lot of that can be done and isn't going to be illegal if they step off the base. So, my vote goes to the wait until it's a pitch, then make the declaration of Illegal Pitch. Otherwise, I think you're gonna have to scramble a little bit to explain what just happened.