I haven't read anything about installing JBDs on the LHA(R) class... as per the illo you posted earlier, the plan is for rolling take-offs using nearly the whole length of the flight deck, thus there would be no aircraft spotted behind the departing F-35B, thus no need to deflect the exhaust away from it.
They are going to back the airplanes up all the way to the stern to start the takeoff roll? Maybe, OK ... Stern of the aircraft at ship's stern, exhaust nozzle horizontal... No need for jet blast deflectors.
Also wonder if afterburner will be needed for heavy gross weight takeoffs?
I'm thinking that a hold back/wheel chocking mechanism may be be needed to hold an F-35 as its engine spools up and the aviator ticks off some checklist items, even if blast deflectors aren't used.
Question for knowledgable Harrier person: what is the standard procedure for a ski jump takeoff? Set jet exhaust horizontal, and mash down on the rudder pedals/brakes as the engine spins up to X percent of nominal full throttle? Do the brakes hold to 100 percent standard power?
Another also: Heating the deck too hot is probably more of an issue for V-22 than for F-35. V-22 cannot rotate propulsion pods to horizontal if wheels are extended. But please, I'm sure the Navy has thought of this, so no need to worry that the deck's going to melt.