is there a easy way for me among others to extend/rebuild/mod. the "old" 3led knob kit from brian to get a 4led "look" to it?

The 4-LED kit has a different circuit board and an extra LED. Perhaps one of the other components is different than the 3-LED version maybe, don't know.

If you asked nicely, you could probably get Brian to sell you a 4-LED board and the extra LED separately.

Another option would be to remove the circuit board completely and use wires to connect the various parts together. I did this on mine so that I could change the positioning of the 3 LEDs. The whole assembly was wrapped in clear shrink-tubing, which I then "looped" around the shaft of the knob. This was very difficult to get working correctly, though, and I don't recommend it. In fact, I still didn't get it perfectly the way I wanted it, and now I'm considering ordering a 4-LED board from Brian and doing it "right".

You could think of your 3 led knob kit in the same way as some people think of their MK1's; vintage! There's always something to be said for being "oldskool", right?