I don't see any problems with having a variable scope on your calling rifle. All of mine do and start at 6X. I like to have the top end at 18X or 20X for the opportunity at a long range coyote. Leave it at 6X on the stand land dial up to what you need depending on distance
If you need to take advice from someone in this, there's no reason to look further than Scenarshooter who is probably the most prolific coyote killer alive.
I've never seen him post a pic of a rifle with a straight 6X scope mounted on it
