is it possible to have a PC "remotely" control the camera using CHDK.
You could if you made some electronics controlled by the PC and providing variable-width pulses.
A script would then decide what actions to perform based on the pulse width.
An alternative method that SDM provides is to run a script in the camera and as soon as an image is captured upload to the PC using PSRemote
For example, this is the complete script for doing that using the SDM time-lapse feature :-
There is no need for the images to be saved to the camera's memory card.