There should be two categories of contestants.
First, the modded category. These will be judged on artistry alone, since if you make it easier to acquire soap, you could as easily be drawing a picture of a fortress. What mod doesn't matter, in for a penny, in for a pound.
Second, the unmodded category. These will be judged equally size and fortress composition as well as aesthetics, since it's as much a matter of effort as design. Do show your number of bars.
However, there is the question of whether modifying worldgen or the init options should count as "modding", since the latter can be simply necessary for some people, and the former is still part of the game "as shipped".
At any rate, I'll be attempting an unmodded Soap Fortress. As soon as my finals are over, so I'll be a week behind, but no matter. I've got a red hot ace up my sleeve for this.