Hi again,
Have you already seen the script that I proposed in another thread? That would be a possible approach that you can take as of today. As long as your application needs an external trigger, then MultiStreamHandler would not have any chance to be used because it does not offer you a chance to trigger the cameras even though you can acquire images at the same time.
Again, we find the reported issue must be resolved anyway but we would appreciate it if you could push your project further with the suggested approach. 
Thank you!