Would be interesting to see this in reality.
I would think a Busa would make a better platform for this though.
The FJR does have an advantage as a platform, what with shaft drive.
I remember way back in the day, when I used to hang out on some hot-rod forums, a guy was thinking of making a standard-layout trike, and was wondering what motors, other than goldwings, he could get with shaft drive...
The main thing I can think of, with the reverse trike layout, is that the shaft drive should be capable of handling the higher power requirements of the heavier vehicle with less wear. Now, I'm sure someone is going to read that and say, "but the Busa makes 1.21 gigawatts, and its chain doesn't break". Well, the busa does make a lot of power, (though the torque is basically the same, FJR and Busa both produce right around 100 ft lbs) but the tire limits how much you can get to the ground. I mean, think of it like this: if you rev the busa up to peak torque, then let the clutch out with any sort of rapidity, what happens? Either a burnout or a wheelie.
If you put a car tire on, that has 5x as much contact patch, on a reverse trike, I would expect a burnout, but you'll be overcoming a lot more grip (and thus putting a lot more load) on that chain before you do.
I believe that the T-rex has a very heavy duty chain, and (from what I've read on the tubes) even then it wears out chains and sprockets faster than a normal bike.
I'm certainly interested in this. If I saw a sweat deal on a front-wrecked FJR, I'd give serious thought to it (and then the reality that I haven't the time or money to invest in it would reign me in).