Sarri has hinted in a recent interview that Hazard has the ability to play in the center of their attack because he can hold up the play as good as any striker around. Whether that means that he'll try to use Hazard as a number 9 or false 9 is anyone's guess.
For whatever is worth he has used Mertens in that role for Napoli.
I don't know about Sarri's plans for Chelsea's squad this January but to me it is pure fantasy to expect that Chelsea would be willing to loan Morata for the reminder of the season. Unless he is really unsettled in London and Sarri wants him gone. If that is the case I expect Chelsea to want him to be sold, not loaned. Or expect Barça to loan him but with an obligatory clause to buy him after the loan ends this upcoming summer.
Also there is Morata's Madrid past. Not sure if he is one of those genuine madridistas that would never entertain the thought of ending up playing for Barça or not (I recall an interview of his where he indeed claimed that he would never entertain such a thought) but I would not be surprised if that was the case. Also as I recall his girlfriend/wife is from Italy and he played his best football (IMO) at Juve so I could see him return to Italy rather than joining us.
Who knows though? So far it's just rumors even though RAC1 is rather reliable all things considered compared to many other media out there. We will see but obviously I would like a loan deal. Do I believe that it is realistic? Not at all. Unless proven wrong.