No. It will be worse.
The accelerometers needs to be protected from high frequency vibrations. placing them in the arms is a bad idea. They would catch more motor vibrations. More they will get wrong acceleration data, because of the accelerations produced by arms inclinations and rotation.
Their best place is certainely where they are actually, on the center plate, on a APM with dampers.
I would think it would require a crazy amount of calibration, too, custom for each build.
I wouldn't discount the idea. I had my IMU in a wingtip and the accelerometers worked. I bet as accels get lower in noise, you may start to get useful rotation data-- where one wingtip accelerates up and the other down. I think the idea is sound, but doing it this way may not be as good as using gyros-- YET.
They might be useful if you used a pair of accello's, one "inside" of the motor and one "outside"? (assuming that the arm is long enough... and you somehow shielded it from the massive EMI coming from the motors)