Skin effect with 50hz yea, no not much.

Ok so every time you change the voltage level you still need a transformer and a inverter to create ac, so no it doesnt make any sense.

Yea have fun transmitting a decent amount of power with 240v over a meaningfull distance. Also most generators produce ac anyways so why would you recitify it at the generator instead of your device after a transformer? You still need all kinds of different voltages everywhere in your electronics and this means you still need to regulate it.

I am not shure how the american wirering worls out but to get from 240 to 120 you still need a transformer… or is it 240v between the different phases and then 120 from phase to neutral?