Here is what you can do that will help get you to your end result.
program a sample file that covers all the basic things..I will illistrat for lathe.
Program a rouging cycle that cuts a profile. Program a finish pass with a different tool that cuts lines and arcs on the profile.
Then program a threading cycle (note program using the Canned option in the dropdown box)
Program all drilling and tapping operations that you wish to be supported.
Now post out the program using the Generic Fanuc MT post. The MT or Mill/Turn post has the most number of already supported options and makes a great base to start from for developing a new post processor.
Now with the Gcode program put notes to the right of the code as to what needs changed for it to run correctly on your machine tool. Save that Gcode file.
Now make sure you have saved your MCX file at this point and go to the help menu and then Zip2Go utility. When the window opens check all check boxes on the lower left of the screen and select the "Create Zip2Go" button.
Once it is done in the file menu there is a Mail Archive option. This will open your mail program with the file attached. Also attach the NC program with notes on it.
Fill out the email and send it to your local Mastercam dealer. This is the info they need to complet the post change request.
Using this info they may also develop you a V9 post processor but with the changes in the system from 9 to X it is wiser to develop in X these days as 9 is an aging system.
You may also want to post the info here as someone here may help you but they also will need this kind of info to complete the changes.
Hope this helps and let me know if you have any other questions.