Elon solution for this is to go much higher then a typical plane. This is much more possible with electric and helps with efficiency.
Air resistance vs not having enough air to push.
Basically - you can design the prop for high altitude, but then takeoff is gonna not be great. You could design a variable prop system (or even have 2 different ones?) but then weight / complexity.
His plane is VTOL so the overpowered engines for supersonic will work well for liftoff.
I don't know how much weight a anti-ice/de-ice could add.
My point was only that once you think about it and redesign everything around the new constraints, you can come up with things that we don't yet think about.