Confusing how a dual Z isn't more popular.
What percentage of the router market do you think has dual spindles? It basically turns a complex machine into a SUPER complex machine. If it were easy, I would guarantee they would be more popular.
I find myself in your shoes- a woodworker learning a new complex tool that requires me to learn a whole new skillset that takes people years in school to master- computer programming. Just shows that the software programs are still in an infancy state and have a way to go to make it so the common man can easily use the machines.
I have to disagree here. You are not just wanting to use this machine. You are wanting to make an improvement to increase your machine's performance. Most likely, you can easily use you machine as it is but it just takes longer than you wish. So there is a subtlety here that makes a huge difference. So to be honest with yourself, what you are really saying is you are wishing there was an easy way that the common man can improve the machine's performance by altering its design. Right?

Well, there's nothing wrong with wishing that. But unfortunately, doing that is gonna require some programming. And possibly electrical wiring too. There is only one Z, one S, and one T in G code so you have to consider all of those implications for dual spindles. Software configuration will only carry you so far once the machine gets our of the more or less "standard" category.
And finally, don't let programming deter you. I too consider myself a common man. Like you, I try to find ways to optimize my work, machines, and processes, etc... It just makes sense. And also because I will freely admit that I'm a rather lazy man too.

The old saying of "work smarter, not harder" comes to mind. Oh, and I'm dyslexic too so maybe I'm not so common. LOL And I will say this as an ex auto mechanic, the very reason I learned to program was to make my life easier. I had a service station (remember those?) and decided I needed to write my own inventory control software. And back then there wasn't much software that you could even buy! No school, no internet, I just stuck my nose in a book, read it over and over, and did the trial and error thing over and over too. Mostly error, BTW.

However, within 6 months, I had my inventory program. Note that I didn't master programming in that time though! But you don't have to master programming to solve a problem. I would say most people never master programming unless they go on to make a career out of it. Adam (DAAD) probably hasn't mastered programming but he sure did solve his problem.
The information I gave Adam was very generic (because his machine was going to be different) and should also apply to your machine as well. Then take a look at his implementation and see how he applied that generic stuff. Even though your machine will probably be different, It will probably give you a leg up to the right path.
Steve