Hi again,
I know it is a really long time since I started this topic and I'm back to show the resolts of my efforts on making the plugin.
After some months working on it on my free time I moved from PIC to arduino as it is less time consuming and some days ago I finally got my CNC working with the system I created. You can see the first test here:
https://www.youtube.com/watch?v=O385I6P_o8oAs you can see the motors do not move perfectly because I used DC motors with low resolution encoders (16 steps per revolution) and the control is based on a PID algorithm so it will always have some error between desired position and current position (about 5 steps) but it has an advantage: it will never lose steps permanently as the PID algorithm is constantly correcting the error.
I am working on some improvements now. Shortly I will post another video milling something and if there is sufficient interest I will release the pluging.
Please note that the controller is not for stepper motor, it is just for servo motors but I do think it's not too hard to adapt it for steppers.