This would be useful in order to share the Display context between subsequent Pbuffer allocations in order to keep the textures when the Pbuffers get lost. Nice, isn't it ?
Unless I'm misunderstanding what you're doing, this won't be necessary. If the pbuffer contents get lost, only contents of the buffers (color, depth, etc) associated with it are lost, not the textures that live in its context. It's a problem only when you're using render-to-texture, since the buffer contents *are* the texture(s).
Could you please confirm that getPbufferCaps doesn't work?