New Biome & Modding Question

Modding tamagotchis is a relatively new concept for me, so I'm really interested in what people who know what they're doing have to say...

It occured to me that even with new Jade biome, there should still be compatibility between the different models. If there's compatibility and tamagotchis can still meet each other and breed with each other, then don't all the characters from different biomes (including the new Jade one) have to be written in in all the models?

Going by that logic could it be possible to mod the three base models to have characters from new biome?