First of all i must admit that i have no idea how game development works, so not sure how doable this is, but what i’d like to suggest, is that instead of having tournaments with a specific creature unlock, we get a chance to unlock a tournament creature of our choosing.
Say if i win a tournament in Dominator league, i’d get a chance to pick one of the tournament creatues to unlock. I could choose Troodon, Gorgosaurus, Erlikosaurus, Mammoth, my beloved Floofy Tyrannt Yutyrannus, etc. Just one creature of my own choosing per Dominator finish. I’d then get that creature’s pack, and it would be unlocked.