It might be the fact that my caffeine levels haven't reached optimum, yet, but I'm not following you here. Why would assigning CVN 77 to Fourth Fleet be special? I'd assumed they would get a CVN anyway.
Jacksonville lost the Saratoga and JFK and is currently not equipped to support nuclear. The Navy pulled out of Cecil Field in favor of Oceania and then, after thousands of homes were built in the area, and businesses were lured into an economic zone, proposed re-opening the field, which was shot down by the voters.
But this is a navy town and is one of the few places in Florida that will not have difficulty supporting nukes.
Non-Sequitur points out that any carrier in the Atlantic would be assigned to the 2nd Fleet and loaned to the 4th Fleet as needed.
My thought is that assigning the USS Bush to the 4th Fleet and basing it in Mayport (and loaning it elsewhere as needed) would demonstrate that the 4th Fleet is meant to be a serious and permanent projection of power in an increasingly troubled area on our doorstep and not simply a reorganization of top brass.