Thanks for the reply.
It seems that this technique would tie the main sketch to OpenGL mode since the PShader() constructor needs an OpenGL PApplet, and not simply an OpenGL PGraphics object. With a library, this is what I was trying to avoid.
Is there a way to get around this: using PShaders without the need for the parent sketch to be in OpenGL mode? Alternatively, circumventing PShaders and going via JOGL directly?