Interesting idea, I like it. It would be pretty easy to implement, but once again I'll need to be able to actually change the BB code to do that, and right now I don't have access.
thinking about it, I just realized that it may requiere some work (lot more than for a flash video include), I mean applet requiere at least a class
file, ok, but lot of time they requiere an archive
and some times they may requiere additional files
... finally it seems pretty hard and it will requiere some tricks/hacks to make it work....
NB : it may help http://custom.simplemachines.org/mods/index.php?mod=48