Okay, I just found a
HUUUUUGE bug. Are you ready?
In the USNI database, the maximum speed of a freighter is listed as
32 knots! In the sim, freighters can do at most 16 knots.
The embarrassing thing is, I actually believed this and tried to put a 30-knot freighter in a mission.

:P Didn't work.
Hey, it wouldn't actually be a bad idea to have a "fast freighter" in the sim, just for comic relief. I mean, imagine an OHP at flank speed, easily being overtaken by a rusty merchant! Priceless...