One of the problems is it has to be rated for high winds; or, you're not going to be able to insure your house if it's mounted on the roof. OK, you might be able to insure it but they might void the coverage if you get wind damage that can be attributed to the panels. Accuracy really only needs to be a +/- a couple of degrees for PV. Hell, most people mount them flat to the roof, which is not pitched anywhere near ideal. some of the larger synchronous motors probably do have enough torque to push over a single panel; and, you can build a cam driven system that tilts the panels in a cyclic fashion. Problem is, if the power ever goes out it's going to be hell to reset all of them. Theoretically, you could use a system that relies on the Sun to heat and expand a liquid, pushing the panels from a "morning" orientation to an "afternoon" orientation. In the end... You're still going to pay more than $200 for a structure with "motor" that's strong enough to do the job and well built enough to survive for 10 years on a rooftop. You could probably make it for a couple hundred dollars; but, you'll never buy it for cost -- you'll end up paying double that (at least) after manufacturer overhead (design and support) is rolled into the cost, and the distributor(s) and installer(s) mark up the price.