Since I got my F5 and rigged it up, I will never go back to a "shoulder" camera again. Yes the FS7 looks like a well balanced camera, and it probably is. Until you change lenses, add a monitor or say a 7Q, or any other accessory on it.
The FS7 has one position it fits on your shoulder. So say the client wants a Fuji Cabrio 85-300, and you're shooting football handheld on the sidelines. You're now very front heavy.
With my F5 and the brand spanking new Zacuto baseplate, I can slide the camera forward and back, changing the center of balance to fit anything on the camera. Canon 30-105? No problem. Swapping lenses and using my 18-35 G&L? Suddenly the camera balance has made it back heavy.....until I just slide the camera forward.
I would rather have 40lbs well balanced that 15 unbalanced on my shoulder. My F5 completely rigged up weighs about the same as my HDX900, but balances much better.
If you want a large sensor camera for under $12K, then this will be a decent investment. But take out the "form factor" part of the equation. Unless you can try it out for an extended time, in the circumstances you normally shoot in, it would suck to decide 3 months later that it really does;t balance all that well, and now you're.....rigging it to balance.