Bad idea. I'll bet some airlines (cough ... Ryanair ... cough) will be tempted to go 4x4 config instead of 3x3. How would you like to be caught in one of those in an emergency situation?
With seats like that, I don't even see how you'd realistically squish past people to go to the bathroom. And how would a little kid "sit" on a saddle without being held by an adult?