you don't really need sysex to use the mackie as a stnadard midi controller.
but to control hardware synths, you'll need it.
the picture with the beat repeat is something a guy made with max msp I think, or was it a self-made application for PC and live 5 (C4!Live), I can't remember.
the soft provided by mackie for the C4, Commander Pro, may allow you to use provided templates for different hardwares and softwares (oberheims, rolands, NI B4...) but the list is not growing anymore. you can customize existing templates or create new ones, but it's XML programmation, you need all the sysex implementation of the synths.
I don't know if it is easy, say, to make a template for NI Massive (sysex? midi?)
I don't know if you can input the text you need for the lcds, when used as a standard midi controller for live...
I don't know if max for live could do the job, I still don't really know what M4L is capable for "merging software and controllers into new machines"...
so many questions
cheers