A few positives of a potential Jack for JT swap -
Both guys have partially guaranteed deals ending in 2016-2017, but Jack's is only guaranteed for 500,000 ... JT is for over 2 million. Also, JT's contract gets bigger down the line, eventually costing more than Jack who's cap hit stays at 6,300,000 every year. JT also has a trade kicker.
Jack can actually make more sense financially depending on how you look at the numbers. I'm not advocating for the deal, just pointing out a few things.
I also think, potentially, Jack is a better fit as a backup 1/2 than Thompson as the FOURTH big. He's a good third big, but no one will take Landry. If the Kings are looking for an upgrade at PF anyway, I can see why they'd swap out for the backup guard. I can see it. Not totally on board, but it can make sense depending on what PDA has planned next.