What I've done when I have code that's not quite right for my machine I load it into a spreadsheet and convert it to what I need. When i bought a new lathe dozens of programs from my older machine needed modification for the new machine's control. Fairly simple in a spreadsheet. I suspect there may be a market for that type code conversion.
Prior to having 4th axis CAM I would generate 3 axis code and wrap it onto a cylinder for 4th axis machining. Sort of a post-post processor.
If nothing else this process teaches you spreadsteeting which is a useful skill to have.
Most post processors I've looked at lately seem to be written the in the C language. Also not a bad thing to become familiar with, although it can be quite a steep learning curve if you haven't done any computer programming previously.
One of my customers uses Mastercam. They needed a 5 axis post so the ball end cutters could be oriented as much as possible away from end cutting. Cost them $15K for that post. Not a trivial thing to write though.