Considering the style of music you're playing, I don't think you'll regret getting a JM. Personally, I have an American Vintage RI, but I have heard good things about the model you're considering as well.
Bridge - I have a Mustang bridge and a buzz stop. This combo works really well. No popping and the buzz stop allows you to have decent low action without string buzzing. I would say that both of these adjustments are almost mandatory. (again keeping in mind your style, the big muff as well). These are both fairly inexpensive mods and you could do them yourself.
Pups - I have the Lollar P-90 in my neck. DEFINITELY recommend. Beefy for sure. Super warm clean tone in the neck-only position. Stomp on the big muff and you can get some real deep, dirty Thurston Moore type sounds. Chords in this position can get muddy, but that's where the my bridge pup advice comes in. In the bridge, I have a Seymour Duncan Quarter Pound (SJM-3). This guy is where it's at. Bridge-only position gives great mids & highs, but still carries the thickness a JM is known for. With dirt/fuzz activated it rings really clearly (my dirt boxes = Noc3 Rock Candy overdrive, Fuzzhugger Algal Bloom, black Russian Big Muff). The Lollar P-90 is RWRP and in the middle pickup position (both pups on), it is hum-canceling. (This feature works with the SJM-3 [and prob a variety of other bridge JM pups], or if you move the stock neck pup into the bridge position). And since you get the hum-cancelling position with the p-90, you could do without a humbucker IMO. I think with a humbucker in the bridge, you'd lose this feature.
Happy hunting.