Direct cyclic control by mast tilting was an itermediate step
in rotorcraft development, like hand crank starting a car.
Once something came along the solved the problems with it
it disappeared.
The problem with mast tilt is very high forces are fed back
to the pilot, in this case the servos.
It seems there is a lot of resistance to a swashplate due
to the fact that it seems complicated, however on a full size
tilt head gyro of the thirties the gimbal that the head tilted on
was huge, big enough to carry the weight of the whole aircraft.
When the swasplate came along, which is just moving the
gimbal off the head and using it to control just the pitch of
the blades, it carried almost no load and could be much smaller
and lighter and cheaper.
The only reason that mast tilt survives today is the bensen gyro
copter where idea was a homebuilt gyrocopter that was as simple
as possible. This kind of construction doesn't scale well to model
sizes, thus the swashplate is still the best choice for model helicopters.
mick