I was thinking of the extra dmx channel being a rate control. It would proportionally scale the current fades in progress. With the DMX channel at 50%, the preset would recall in all it's associated fade time. Changing the dmx channel towards zero would proportionally scale all running fades, equally changing the dmx value towards 100% would proportionally speed up the running fades.

0% = stop
25% = Fade time doubled ( i.e. a 5 sec fade would be 10 sec )
50% = unmodified fade time ( i.e. 5 sec fade would be 5 sec )
75 % = Fade time halved ( i.e. 5 sec fade would be 2.5 sec )
100% = snap

This approach is different to the idea of a timing channel that is found on moving lights.

I only had this idea, as in our situation it would be useful, but in the long run I would prefer a console that enables me to program the layers from the console.

Andy