Wait and see
There's a plan to release the skeletal models (WarBoss and Xan II) along with some utility stuff to make model-making easier. This will probably include my fixed versions of the models, so they'll be skinnable too.
This may even be in the next official UT patch, although this hasn't been confirmed (so don't quote me on this).
As for downloading, use Download Accelerator Plus and leave it downloading in the background. Some of the maps in Bonus Pack 4 are very cool, so it's worth getting it (and all the other bonus packs for that matter) anyway. I downloaded them all on a 56k modem, it is possible