At the moment we get $25 a story, and with stories averaging out to around 5000 words, that's 0.5c a word.
For this volume, how about 0.25c a word, rounded up to the next cent. So some-one who has one 300 word piece accepted (the minimum) gets 75cents, whereas someone who gets three 1500 word pieces accepted (the maximum allowed) gets $11.25. If we do say 0.5c a word, then the first writer gets $1.50 and the second $22.50. Ditto for any poetry.
Anyway, like I said, just an idea.