Is Malins any good in the air or at last ditch tackles? Those are Daly's weaknesses and that's what needs fixing at fullback. Otherwise, we gain nothing by putting Malins in there over Daly. Didn't Nowell play a lot of fullback earlier in his career? I'd like to see him given a shot, he's got all the skills (albeit no size). And Watson is proven there to my mind, but not a playmaker like Daly, and that's what Eddie likes there.
I also think Eddie's in a bit of a tricky position with Saracens. I don't think he can select players from the Championship, so he won't want Sarries to go down or he will lose a big talent pool, so when it comes to selecting promising youngsters from Sarries like Malins, Earl, Kpoku, Isiekwe etc, if he takes them as well as Sarries' England regulars for the 6 Nations squad, he's pretty much guaranteeing Sarries will lose their Premiership games during the 6 Nations, coz they'll be down to 3rd-stringers for the most part. Given that there is a Barbarians match and a 2-game tour of Japan coming up (and that Eddie has hinted he would rest his World Cup squad for the Japan tour (IIRC)), I think it likely he leaves Sarries' youngsters out of the squad until then. He'll pick some new young talent like Hill, Dombrandt etc for this 6 Nations, but given Sarries' issues, together with the overall youth of the England squad anyway, I don't think we'll see more than half a dozen, and probably mainly at problem positions with not much depth such as 3, 8 and 9. Otherwise, there ain't a lot that needs fixing.