the main thing that just seems to get over looked is just thinking about intercoat clear as basecoat clear like you are saying. I also refer to it as flake carrier.
I am not professional enough to answer, but to me the most important part of using intercoat, or basecoat clear is that it dries within 20 minutes and within a half hour or hour you can tape for other effects. You do the entire coat with your topcoat clear, its spray it, turn off the fan and walk away til the next day. You dont like the effect with the intercoat, you mix more flake and add another coat, right then until you are happy. Its also good to add depth to work between shading when you are concerned about taping on top of your happy place..
I have added flake, candy to intercoat, basecoat, topcoat clear. I have also added candies to the first coat of the final clear, never all the way to the end, so its all uv protection on top.