I have a highway 1 J that came with a BA, I have a MIM J with a babicz, a US J Plus that came with a QC schaller, and a mongrel J with a fender L plate with threaded saddles.
If you are looking to make the kind of changes you mentioned you will be throwing your money away to change the bridge. I like big gaudy bridges because I grew up playing peavey basses that always had big gaudy bridges on them, and because of my playing style I tend to pull much harder on the strings than need be when I play fast and a locking bridge helps keep my strings from wandering when I'm trying to rip them out of my bass.
If you have a serious problem with strings creeping latterly when you play, a locking bridge may be of some practical use to you. Otherwise a set of threaded saddles will improve both the looks and function of your stock bridge and save you enough money to snag up a set of Model J or Area J pups, either of which IMO will go much further toward reaching your stated goals regards the sound of your bass.
Unless this is one MIM J replacing another and you are already familiar with MIM J characteristics, why don't you just play it for a while before making any changes?