Should we ban the Griffin Conservatory and the Hive of Serpents?

It didn't even take much effort here. It's a perfectly logical continuation of your idea. And it is quite competent (for the goal they set), as far more nuances were taken into account than in yours.

Since there are no free angel-ducks, you accumulate troops for taking the Dragon Utopia with great difficulty; you manage to get in on the 3rd week if you're lucky (though usually the 4th is needed), and you lose a significant portion (well, it's a weak army, there are no tanky stacks like angels and vivs), and as a result... you're out of luck, time to surrender, because even if there are enough troops for a second Dragon Utopia, they will be severely depleted there. Dragon Utopias must be banned, definitely.