The idea certainly sounds do-able.
In order to drive the stage in the pattern that you want, you will probably want some kind of PIC or Arduino or other microcontroller-based stepper motor control unit, which sends pulses to stepper motor driver boards.
There are circuits used for robotics that could be modified to do the job, or you could look for projects such as "rotary table indexers", which could be modified to do something similar.
How much accuracy do you need in positioning?
Maybe you can integrate shutter control of your DSLR with the stage movements so that all you have to do is push one button.