JFK would push for civil rights, too. With that, Goldwater either gets a "Southern moderate" or a former Democrat like Smathers or somesuch to begin the Southern strategy.
I suspect Johnson would be dumped in 1964 for the same reasons Agnew nearly was in 1972. With him gone, JFK chooses Symington for great foreign policy experience.
He might push it, but he'd get no where with it.
JFK already has foreign policy experience.
Dropping LBJ, means losing TX. The fact he was in Dallas on 11/22/63 means he had no plans top lose TX or drop LBJ