My tone arm project uses servo controlled captured linear tracking wand, with a laser to adjust the arm for warping and off center pressings, driving the cartridge perfectly though the grooves. eliminating much of the variablility in different pressings. The laser will also detect exact VTA setting for each LP and make real time adjustments should they deviate more than the allowable 1/10 of a degree.
The servo's can be set for the three common High performance stylus tips and any cartridge tracking force. An algorithm "evaluates" the laser gathered information from the LP to assure that the cartridge only sees tracking forces +/- 1/1000th of a gram and detects and corrects mistracking momentum predicted by the cartridges known mass and center of gravity.
My system does not rely on gravity other than to keep the turntable on the stand, this system could theorhetically with a few provisions in the software could play lp's upside down.