Flipchan,
Thanks for letting me know about Layerprox. I hadn't heard of it before.
Currently, as you probably know, Marionette does one format at a time. However, Marionette is hierarchical in its format construction, and therefore we can do random selection between formats by considering each format as a 'sub-format' of the overarching format. Look at web_sess443 in our current release as a way that this might be done.
As we continue to go forward we will be updating the formats. Exactly when depends on funding and other priorities. We recognize that an update is needed. You don't have to wait for us to do them, though. If you make a format we would be happy to consider it for integration in the repository.
If you want to put a wrapper around Marionette to give it extended switching ability, we have implemented the PT2.X standard, so feel free to integrate it into your code that calls it. Just let us know that you have integrated it, so we can add you to our list of people that we have integrated with.