I understand what you're saying.
But, just from the way DP has acted, I don't think he planned it. I think he killed Stacy in a rage over something. Then, he had to think of a way to dispose of the body quickly. I don't think he had time to think of any diversions. He disposed of her body, and then came up with the "she ran off with another man" statement. If he had planned it, I don't think he would have planned on killing her in the house, especially with the children present in the house......he would have thought of a way to get Stacy to go with him somewhere, or meet him somewhere.
Since the beginning, DP has been very transparent in his actions, and I have the feeling that he's making it up as he goes along - not that he had planned it. The letter he supposedly received from a tipster is one such transparent thing. A genuine tipster would be calling LE with their "sighting" of Stacy in the Kroger store in Peoria, not sending DP a letter.
What we've seen of DP, we know he's a very bad actor and not good at planning. He had time - a couple of days to prepare for the interview on the Today show. He's a policeman and should know how people react to bad news about a loved one. Yet, he couldn't even muster up some fake tears or fake emotion. Instead of going on that program and crying and pleading with Stacy to return to her family and saying how sad and upset her children are without mommy, it was all about him. He couldn't even act like a grieving, jilted, spouse.
When it came to the exhuming of KS body and the second autopsy, he attacked the findings of a medical examiner, instead of acting surprised at hearing that his ex-wife's death was a homicide. DP isn't good at planning things to make people think he's not guilty of wrong-doing.
I'm just not sure if DP is smart enough to think in terms of planning a diversion.