Yes, I have also done this.
I have copied the original one with 60fps, assumed it as 30fps, and incorporated this into my project which mainly consists of 60fps snippets.
I would like to know, how will this affect the quality of my final render? Usually when you reduce frame rate from 60 to 30 and then export it as 60fps again, the 30fps footage will look a little bit weird.
I am not quite sure how PP is handling these things.