for the end date of the competition, i think 2 weeks is sufficient time for people to develop card ideas.
for the number of submissions per person, i would personally allow for a cap of 2 ideas, each with an up/unupped card
but a good question is are we looking for innates, perpetuals or both? given their relatively little difference, id go with both.
unless we differentiate innates and perpetuals by requiring a perpetual to be a theme shared by many creatures, such as airborne, and force non-theme non-active abilities to be innates?