Modifying Spawning Conditions for the new wolf variants and armadillo

The new wolf variants and armadillo mob are very unique and interesting. The only problem is that these new mobs can only spawn in biomes which are newly generated. This means that when updating premade worlds, these new mobs can be extremely difficult to find. For example, my 2 year old minecraft world is completely surrounded by the savannah biome yet this biome is empty when it comes to the spawning of armadillos. Same goes for all the other biomes which the wolf variants spawn in. The main problem at hand is pre-loaded chunks are not generating these new mobs making it more difficult and tedious to go find them. I propose a feature in which these new mobs are able to spawn in pre-existing chunks to allow a more fair and fun way to go exploring for these new mobs from the armored paws update.