LLVM-pipe: most powerful instructions set ;)

First, thanks for saving my day. Software renderer works way faster than 
no renderer at all :)

But there are an "instruction set" which is way faster than the MMX or 
SSE sets: it's an existing OpenGL 2.0 driver which is not sufficient in 
most cases, because at least 3.0 is required nowadays.

Of course, it's not literally an instruction set, but a source of 
additional computing power for basic operations (assuming advanced 
operations are not supported by the GPU, making LLVM-pipe necessary for 
such systems).

So, the actual question is:

Can LLVM-pipe somehow support (today or in future versions) a "bridge 
mode", relying on a different OpenGL driver for basic operations 
(supported by some ancient GPU) and closing a gap between that driver 
and the required OpenGL version it's usual way, by the state-of-art 
software renderer?

It's also somewhat related to my OGLOED driver idea (see my Github), the 
difference is "bridge mode" is local, OGLOED is not. But there are some 
diagrams which can help understanding my question :)