To pass in your own NetStream, you'd need to define a custom NetLoader subclass that overrides the createNetStream method, and use that object as a parameter to VideoElement.
To pass in your own NetConnection, you'd need to create a custom NetConnectionFactoryBase subclass that returns your NetConnection in an event when the create() method is invoked, and use that object as a parameter to your NetLoader.
There's no "official" way to pass in your own Video. However there's an undocumented (protected) createVideo method on VideoElement, which you could override to return your own Video object. (Note that any undocumented API is subject to change, so you should try to avoid relying on them.)
your solution sound pretty complicated. I already subclassed the NetLoader Class to make the call to the FMS successfully, but now the next problem occurs. The stream stutters and hangs when the fms changes a video in the stream. I hope this can be solved too then i won't need pass my own Video object to the fms