Perhaps the car makers will come up with a hybrid powered liftgate, like how a DSLR lens has the A/M switch where the lens will autofocus but you can always grab the focus ring anytime to override it. It'd be great if the liftgate can be opened manually (and freely), and the motor only engages when requested (button, foot waving, ...). Of course, they'll also need to design for user errors, such as pulling/pushing on the gate when the motor is closing/opening it, too. That probably won't work for the mass, too many potential lawsuits?