[heimatau]

Great questions.

Tesla's problem isn't by intention. It's by NEC (and local) code requirement.

For the second question, why not lay it across the sub roof: Water can be very damaging. What insures those wires (over 20-30 years) will not be damaged? For a conventional solar installation the wires are elevated and protected due to the cavity of each panel. Local codes generally require that no wires touch the rooftop, so that prevents the daily ware/tare.

As for the latter idea, I do believe that's Tesla main goal. But to practically do this is an engineering feat that hasn't been solved yet. Can Tesla do it? Sure. But I haven't seen them invest in a solution yet. Heck, Elon is focusing on too much and not fixing this issue. It's okay, he's got bigger fish to fry. But since it's not solved, they will continue to live with this problem.