I have a couple suggestions:

1. Make sands and oils limited to 1 per week. After all, CT limits you to 1 oil and coil you can only get maybe 2. It seems ridiculous to have unlimited amounts.
2. Make it that once you've killed 1 A/S rank per week, you can not kill it again until the following week. This way everyone gets a chance at every S rank weekly without all the fighting over the same guy over & over.