Smeagol, on your post about the wide range of SF subjects, I definitely understand your point.
Though I haven't participated in any contests, the main point I see that causes some of the issues of judges having "NO IDEA" what to do with those models would seem to be what I've heard of regarding accuracy.
If the number of posts in the SF part of this forum is any indicator of interest among modelers in general, I'd guess that there are few judges out there who really know enough about SF subjects to judge on "accuracy" of a SF kit. A model of the Space Battleship Yamato may have the added weathering touches and customized details to make it look as realistic as the 1:350 IJN Yamato next to it, but I doubt the Space version would even be considered for comparison to the "real" ship because of the fictional nature of the subject.
That "accuracy" issue is why I had SF in a different category in my suggestion. Even though you'd likely still have a problem with judges unfamiliar with the genre going by technique over what us fanboys could nitpick over regarding in-canon accuracy, at least that would leave some kind of standard most experienced modelers could understand.
Probably the least debatable area to mix "real" and SF subjects would be figures. If it were up to me, I'd leave the mecha you mentioned in the general SF category ( again, because the weathering and detaining techniques used on a Perfect Grade Gundam would have more in common with how you'd weather the Millenium Falcon than how you'd add depth and texture to most figures ) and leave characters in a figure category. The main problem I can see there is when you would have something like WWII soldier in uniform next to some of the anime character figures.