What if every week, we had a strike event that rewarded 5 of either feed, interact, or play items, much like stat boosts? For the respective item rewarded from that week you could face a group of opponent dinos that give the most DNA when given that specific item in a sanctuary. For example:
Food Strike: Rex, Irritator, Dimetrodon
Play Strike: Carbonemys, Tenontosaurus, Triceratops
Interact Strike: Nothing really likes interact more than anything else so I guess anything could fit. Pterosaurs maybe?