Aight, here's my two cents on this.
Doing something like this would require a large amount of restructuring, simple as that. I have played on three servers that have had this type of system, with myself doing both sides on two of them. Its a great system, don't get me wrong, It allows people to do what they like and not get burnt out. But, the problem here at Synergy is not particularly the GM/Staff system, its more of the amount of time spent in the current system. You simply can't just do this out of the blue, when you pick a system, you're stuck with it, especially at the scale we run.
I'm not opposed to the idea, but the restructure would be a massive fucking pain in the ass for everyone involved.
The system you suggest works great for Superior Servers, and it would work great here too, if only, it was implemented at the start.
But, hey, its not my job to decide whether this goes through or not, and how it will be done if it does go through.