trailer = couple organized players with access to the new mod or craftly make others think about the new mod by hints and suggestion, easily done.
new intro = 1 player with enough vid clips to put it together and cut scenes to incorperate into a 3.5 min video clip and make everyone drool.... easily done.
movie = several ways of doing but none easy. would require several people for voice overs, 3D modeling and rendering software to incorporate not only ship mods but characters as well. sound effects, music, time patience and energy from every participant, not to mention a decent script and and eye for scenes.
I vote Trailer and just make enough cut sequence to hint at the new mod and give suggestions to what has been announced into the new mod. Highlight the good points, and please dont do slop 120x80 resolution as on any machine it looks like garbage unless its for an avatar.