I'd get him to train 24/7 with Askren. Challenge is to tag Askren without being taken down. Once he does get taken down, just reset and get back to work. The only way he wins this fight is if he gets mobile enough to avoid Khabib getting hold of him, because once in close enough he's going down. You can't just make up for a lifetime of grappling in a few years, no matter how hard you train.
But more than anything Conor has to regain his hunger to have any chance. I think he peaked against Aldo, the build-up and mind games culminating in a spectacular knockout made him a star, it went to his head and he's never trained as hard since then. Before he was obsessed with improving, now he's obsessed with marketing and fame. He got a bit of spark back with Diaz 2, but I think the money has killed his drive.
He may never beat Khabib even at his very best, but in his current state of mind he has no chance.