And by doing most of these you also have to include an alternate independant electrical system. I've had a complete electrical failure in an a/c. No drama at all. The engine didn't miss a beat. It couldn't because it wasn't involved.
I've had a fuel solenoid go tits up in my car but not in an a/c.
Certainly there are some good points in what you've said. Fuel storage particularly. There's no difficult reason why tanks can't be directly connected, effectively making one or two large ones.
Countering that is when fuel is used as ballast for balance. It's damned convenient to be able to isolate an advantageous compartment.
Ditto throttle/prop. interconnects. They would simplify things. Until you hop in a piston twin when having fine manual control is needed to sync. the props.
Mixture could be fairly easily automated I think. Perhaps with a barometric/temp. device?
Personally I like having a reasonable degree of manual control. I regret the loss of my car's manual choke & prefer manual gearboxes.
Perhaps my arguments reflect more my personality than anything logical!