If the Borg were used as a character many 'extras' could be in the background but not just created as a CG character but using a AI model created in a videogame engine
so they wouldn't have to be animated.
Actually other alien and human background action 'extras' could be done the same way.
It would add a lot of production value.
In Star Trek Nemesis
on the SCE DVD the visual effects guys spoke about creating Romulus as a CG model during that big flyover and then having to add animated characters walking around.
Motion Capture is one thing like it was used in Resident Evil Degeneration
in this behind-the-scenes video about the MoCap in RE
but now these characters could be