Thanks for the reply.
Here is what I can already do using the 4 cable method:
1) I can set up a patch with out a modeled amp or pre-amp and just use the POD as a stomp box substitute.
I have some effects running into my pre-amp like distortion etc. I have some effects in my loop hitting only the power-amp through the return. In this mode my knobs on the Cornford still work. I can adjust gain, tone and volume.
2) I can set up a patch with a pre-amp model, like a blackface for instance and an FX block. Now I'm by-passing the pre-amp on the Cornford. I have confirmed this by trying to adjust the gain and tone stack knobs - no effect, they are bypassed at this point.
So, example 1, I'm putting signal into the pre-amp and the power amp. Example 2 I'm putting signal into the power-amp only.
If I'm only putting signal into the power-amp there is no need for the cable that goes into the front of the amp. All I would need it the cables in the FX loop.
This is why I think I should be able to select the output configuration by patch, not be locked into 1 mode.