While both the ramp and the lift have their dangers I think the ramp is a little more dangerous to the robot being climbed specifically if there is a arm or tube manipulator it. This can be prevented a little easier with something to keep the lifted robot from swinging into you.
Also, as far as pnuematics being too weak to lift a robot, (which, as its been said they are not) there is nothing ruling against aiding the piston(s) to lift a robot, such as gas springs or a pulley reduction
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