Yah, from aviation everyone moved to twins because tri-jets and four engine jets were too expensive in comparison. Things don't scale up or down perfectly; in practice you end up with more maintenance.
But it seems like here they lost steering, so maybe there's something better we can do to keep steering more of the time (the cutover to emergency steering gear isn't instantaneous or perfect).
Not just for a while. They must be able to do so indefinitely, until you run out of fuel. Of course, you are going to want to get it back on the ground long before that happens.
- The current accident rate due to lack of redundancy isn't too awful.
- Adding redundancy increases cost, even when it seems like you have the same total power or whatever.
My bias is towards a bit more redundancy than we have now, but not massive changes.
Redundancy doesn't inherently have to cost a lot more. For example, if you have three engines driving three props, they can each be 1/3 as large, and not necessarily weigh much more if at all. But then if you lose one, you lose 1/3 power rather than experiencing total loss of control.