If you think about how it works, a wire pulled and pushed from the motor goes one way to rotate the upper arm anticlockwise 45% from horizontal and the lower clockwise 45% (Hp2) from the vertical, and when the motor switches the other way the upper arm goes clockwise 45% and the lower anticlockwise 45% (Hp0). If you wanted to display Hp1 you need both arms to rotate 45% anticlockwise.
I can envisage some clever cam mechanism that could achieve this with a single motor - fire once Hp0, second time Hp2, third time Hp1 then fourth time some invalid position with upper arm at 90% lower at 45%, fire again back to Hp0, and so on. Or perhaps better a cycle of Hp0, Hp2, Hp1, Hp2, etc. But it would take some clever mechanical engineer, cleverer than me anyway, to work out exactly how to do this. It would be a good exercise for an engineering student.