In short - NO. Only one "master" controller board can be used. It's clearly described on the website - http://simvim.com/svc_structure.html
The system is extendable with method of addition various extension boards, including slave controllers (as servo, steppers, button matrix, PWM, etc.).
We actually went back to our old ArdRef interface very effective architecture, but on new level.
1) First, you couldn't move to SimVim using the all ArdSimX configuration and connections, it's completely different systems. SimVim allows you to make it "from scratch" very quickly.
2) Method of inputs extension used in SimVim is much cheaper in terms of "investments" - for the price of one additional mega you can have 150-200 inputs and much cleaner, modular wiring.
3) Using one Master board eliminates the auto-connection issues that can be with using multiple serial devices. And, several boards would need much more complicated configuration tool, because SimVim system has more complex internal algorithm than ArdSimX.
We only may consider adding support of more additional devices and boards.
Vlad (father is me )