I'm going to stick out my neck, and try to answer your question in an indirect way.
If I understand the purpose of using BufferStrategy, that is to get better performance. Doesn't trying to use buffers in system RAM ruin that perfomace gain? Why not just use the old methods of creating off-screen buffers?
I see BufferStrategy as a way of encapsulating rendering, whether it is vram accelerated buffering, or simply a back bufffer in system ram.
As for the issue about speed - there are certain circumstances where you want to use a back buffer in main memory.
I know you can create the back buffer in main memory using the traditional method, I just thought it'd be alot neater if this functionality was encapsulated within the BufferStrategy class.
It even looks like this was the intended fuunctionality, as the ImageCapabilities class is used to define the desired capabilities of both the front buffer, and the back buffers.