1-Possible: Yes, Implemented: No -- Although you could "trade" the visualization support in order to embed the Video window in it's place if you wanted. You can most definitely add the video extensions on the music section of RRConfig, then you should be able to play their audio portion at will.
2-Double Click the Vis -- if setup right it goes Full Screen. In AVS, 1 touch of the screen returns.. in MilkDrop you have to set a different resolution. Please do a search on visualization plugins as there are plenty of threads about it.