I hope Bobby forgets this prequel idea. For one, I hate prequels, I already know where the story will go eventually, don't need to see anything else from past.
Secondly and most importantly, it would ruin how I view Kathryn if she has had this crazy past. I view her as someone sweet, loving, a bit naive, bit not someone that would go on crazy sex adventures.
So yeah, hope he scraps this whole prequel idea and just focus on a new cast. As for her showing up, I would be ok with a small cameo, maybe based on paths, she shows up with Luke, alone, or whatver type of paths we got, just a small scene, can acknowledge her, then move on.