I agree with most of what pvgirl said. I would skip the 6 gauge wire to the PV strings. I don't see the point. You are better off running 1 1/4" conduit and use 10 Gauge wire and when you pull in the wires leave in a pull string in case you want to change or add conductors. 10 Gauge is plenty for your projected load. If you price 6 gauge THHN vs 10 gauge you will rethink your wire choices.
So your scheme for moving loads to the solar system is simply to wire them to the 150amp panel rather than the 200 amp panel? Are those two panels adjacent to each other? I thought they where in different parts of your house??
Regarding the mechanical structure for your ground support system. The locations where you use U bolts to secure the cross frames to the tube; You want to get rid of the U bolts. They will slip. Instead make a weldment that attaches (is welded) to the main tube and bolts to your verticals. Also, rectangular tubing is probably a better idea than square. Steel is cheap compared to everything else, overbuild rather than suffer from structure failures. I would have someone run some mechanical analysis of your steel selections. Pillow blocks to support the frame may be overkill. There are a number of ways to allow a pivot without a ball or roller bearing. I would think that a detail of the foundation of your vertical post supports would be required if this is going to be inspected. Rather than putting an actuator on the 2" schedule 80 main tube, I would consider a hand cranked screw with a lever arm, unless you are going to level the assembly automatically if the wind pipes up.
Anyway, nice plans.
Are the net metering rules where you live favorable?
Thanks,
Dave