The only way this fight makes sense is if Jones loses to DC (and it's not controversial or a barnburner).
If JBJ wins, then his aura will be intact, so why risk that against a guy who will likely never fight again and is tainted himself? I'd pick even a diminished JBJ as the favorite over Brock, but it's too great a risk. Jones' greatest asset is his credibility as a fighter, because he's one of the greatest fighters the sport has ever seen and definitely the best LHW ever.
If Jones loses, he still has that legacy but his peak will be officially over, and putting him in a freakshow fight to make one-off huge sack of cash makes more sense.
However, I have a feeling WME is run by retarded monkeys who think fight outcomes are pre-destined and that Brock is "canon fodder". They'd probably book Ronda vs. Cain Velasquez if they could.