Well, since there would be monthly contests, why not make 'themed months'? For example: one month of F/F art, then one month of F/F stories (or together), then a month of M/F...
Though, there is a problem: would the artists pool be big enough to cover such a large number of categories? I mean, seeing how some artists like to write F/M, some like F/F, etc. I'm afraid that would leave us with one or two competitors monthly, everything taken into account. Also, dividing between anime and western art would make it even less people per category. I'd suggest to run the 'all-around' test tournament, where all of the artists and writers, of all the gender and art categories would compete, and then see how many people will actually apply. Then, using that number could future groups be created accordingly.
So, I suggest we make a general competition first time around, and then split if the numbers allow. You'll probably need to know how many people will compete (I, for one, won't).