Hi Paul,
If it works I might be tempted to leave it as it is, although I do agree that with the 2K the ability to run each independently would be an excellent benefit.
I recently completed an install into my new 1k, but with a Lenz Gold Maxi, Uhlenbrock Intellisound 3 SUSI sound module and a Lenz power buffer.
I kept the original LGB electronics. I did do a few extra things to make the install neat, make sure it would all fit in and reduce the possibility of pinching a wire.
1) The wires from the LGB board to the firebox light and cab switch are stupidly long. I reduced them in length and resoldered to the electronic board in the firebox. (Incidentally on my model the firebox light had a three pin plug on it, but pushed into the four pin socket on the LGB main board! Although I had noted what went where, I neglected to note which of the three pins in the four pin socket the firebox light was supposed to connect too, and the first time I put it back together I got it wrong and nothing worked!).
2) I snapped off the extended circuit board under the screw terminals on the decoder to make it slightly smaller.
3) I made my own connecter for the DCC interface to the screw terminals on the decoder and cut the wires as short as I could so there was no excess, and the decoder was held where I wanted it in the centre on the top of the speaker. The Massoth part could have the wires lengths reduced as well.
4) The power buffer (I agree not needed on a 2k, but could be necessary if the locos of the 2k are run separately) fitted nicely in the space by the firebox, as did the SUSI sound board.
I thought I might do a quick report on the Dietz/Uhlenbrock SUSI sound module sometime when I have a little more time.