Board Thread:Speculation House/@comment-27511601-20170107190552/@comment-26397825-20170710093900

I think the original trailers were made quickly more as a proof of concept, and then the designs for the characters (at least, Ruby, Weiss, Blake, Adam, Yang and JMM) were sort of set in stone and couldn't be changed for the show itself. While Blake and Yang's trailer were plot-relevant, Weiss's was more of an artistic flashback and Ruby's was literally just a "look at this cool thing I did" than an actual trailer for Ruby herself.

Add in the fact that RT's animation department was very poor in the early days...I doubt they even had the knowhow or people to make their own models for every character and weapon. It's sucky that they grabbed freebies from elsewhere, but the steps that led them to doing so are at least understandable.