Cool that someone else has been thinking about it. I figure that a full-time electro-hydraulic setup could be done without too much hassle, but like you said, if the return on energy draw is null, then why do it. I reckon the way to go is a demand system, like on the newer LX platform MOPARS, such as the 2011-plus Challenger. That's a nifty setup with a conventional hydraulic-assist rack with plumbing, with a demand electro-hydraulic motor. I love pulling into the garage in the Chally...with each steering movement you hear the whirr of the motor...kinda like the terminator robot noise every time it moved an arm or leg.
Had even thought about taking a tilt/trim hydro-electric setup from like an outboard motor and toying around....not sure if it could hack the duty cycle, but it's cheap, attainable (versus aircraft demand pumps, etc.), and someplace to start.
"Hit em' where they ain't"
Roy D. Chapin Jr.