Is there any chip or very minimal circuit to achieve this?

Yes, it is called a microcontroller. With an 8-pin PIC, the circuit would need only a single 100nF capacitor in addition to the chip.

 

Preference that results in an inferior solution is not a good idea.

I felt microcontroller is overkill for this. I got to try first to decide on route to take.

 

This is basically what I am trying to achieve.

A circuit that takes 2 inputs A, B and
When
A-0, B-1 = Move servo to 0 ;
A-1, B-0 = Move servo to 180;
A-0, B-0 = Move servo to 90 (default position).

For the last, the servo is always should automatically reset itself (to 90) when A=0, B=0.

 

I felt microcontroller is overkill for this. I got to try first to decide on route to take.

It is likely the smallest, cheapest, least complex, and most flexible solution. And I, at least, would have been done days ago.

Using a 32-bit 1GHz microcontroller would be overkill.