export complete os/x keymap in xml to programmatically modify, then import

I would like to programmatically create a keymap for pycharm. I have an ergonomic keyboard for which the function keys are very awkward to hit. I'd like to map everything with a function key to something with a prefix, so for example, (I'm on mac os/x)

Command + Alt + F7 

will go to

Alt + J
Command + Alt + 7

That is I'll use Alt+J as the gateway into my remaps for function keys.

I can do this on an action by action basis, and I've found a xml file at

~/Library/Preferences/PyCharm<xx>/keymaps/

but it seems to only have my new keymappings. It would be great if I could export an xml file with all the keymappings, and then create my alternative mapping from it. Anyone know how to get a hold of such a complete xml file of the standard keymap?