Suggestions on how to improve sketch request selection (Patreon)

It seems the method I used to fill the sketch request slots lead to some issues, especially with the... funkiness of the Patreon app, connectivity issues, latency, etc.
I'm not sure how else to fairly select the 15 sketch requests aside from some raffle (which appears to be against patreon rules?).
If anyone has any suggestions, I'm open to hearing them to try to improve everyone's experience!