Yea the foot reach would be tough. But thing is Jones has little KO power standing. So Cormier would walk through them to get a TD.
Can Cormier get Jones down? For sure I'll take the Olympian any day is that aspect. Cormier could take Barnett down any time he wanted.
The real question is could Cormier make 205 in a healthy manner? His kidneys had failed because of his lifetime weight cutting.
I think Jones' wrestling is enough to nullify a TD. Hell, Jones has tooled very accomplished wrestlers. Jones may not have one shot KO power, but he'll beat you to a pulp until you quit regardless of how tough you are (see Shogun).