Well, I believe you could extract the net files
…and then try to rebuild that jar from the command line with – either directly with javac, or with ant
…and then put that net2.jar library in the Processing contributed libraries area and call it by its package name from a sketch rather than calling the built-in net.
I haven’t done this, so I may be missing some details.
However, I honestly don’t think that would be easier than following the setup instructions on Eclipse. It actually might be significantly harder, as both the Processing repo and the Processing Library Template repo have Eclipse configured to do a lot of really complicated building for you, including the integration of the net library with other components and where to put the outputs.
Also, more generally, one often thinks it is “one change, one time,” but in my experience it almost never is – especially when that proposed change is untested. Being set up to make further changes really helps. An alternative is hiring a developer to do it for you, and being able to have them test it and go back to them if it doesn’t work. I personally prefer DIY.