It is also intended to be a VTOL aircraft for the Marines, a carrier fighter for the Navy, and an export fighter for the RAF. It is expected to act as a fighter when it is not playing bomb truck. (A job the F/A-18 does very well already)
The last time we tried to build a plane that versatile (that is, a design by committee), we ended up with the F-111, a disappointing aircraft about whom a USAF general once said "The only good thing about the F-111 was that the damn fool Russians went and copied it." (He was referring to the Su-24, an even more disappointing aircraft)
The best planes are first and foremost good flying machines. If you have a good airframe and engine combination, you can get a plane to do a lot of different jobs by simply cramming different avionics and weapons in it. Witness the F-15E Strike Eagle. The F-4 Phantom. The Corsair. We had a really good flying machine in the Raptor. Economies of scale would have driven the price down if we hadn't abandoned the program in favor of the empty promises of the F-35. The JSF is NOT a good airframe. It has only one engine, which is normally slower but cheaper...but we contracted to two different suppliers to build two different versions, so it wasn't cheaper, and it is still slower. It uses a horrendously complex system to achieve VTOL flight, which should insure the mechanics are kept unhappy and cancel out any sortie rate benefits it should enjoy from being VTOL. It will not be able to remain stealthy while carrying a bomb load any larger than the Raptor. Since its primary role is bomb truck, and the greatest need for stealth is when approaching a target, there seems little point in suffering the expense of a stealth design on an aircraft that was supposed to be cheap. We are going to end up with a plane with one less engine and shorter range than the Navy likes, a VTOL hangar queen for the Marines, and a fighter-bomber for the USAF with the price tag of a Raptor and performance little better than the F-16.