Hello, long time forum lurker and avid trader here. I've been silent with everything going on but I'd like to share my 2 cents right now.
I do like the idea of adding new categories for rarities for pets, but doing so raises other concerns. I like to put myself in the shoes of a brand new player when thinking about things like this. While trading would absolutely be easier for a newer player with the new categories, I think that it would also make things much more confusing. How are they going to understand the difference between a Extremely Uncommon and Rare? What IS the real difference behind them, in a trading perspective?
In my opinion, with adding 4 whole new labels for rarities, we would also need a site wide guide and understanding to trading these new rarities. Hot take, I know, since a lot of players are against trading guides/lists.
In the perspective of an older player who mostly only trades and doesn't care for anything below the rarity of uncommon, I'll trade a 2013 common for some newer one, because they're not worth much to me. There is so so so many pets on this website, and the majority of them will never be traded, or they will sit in the pound because otherwise they'd just sit in someones unsorted or random pet group. There is no incentive to trading these lower commons, there is nothing we can do with them besides look at them. And the likelihood is - everyone else probably has the same pet.
What I'm trying to get at is that it's a bit.. insignificant. I'm not trying to be negative, this is just from my viewpoint. But creating all these new groups for pets that likely won't be traded (unless they're older pets) is only going to create more issues (IN MY OPINION) with trading.
I'd like to instead propose different monthly adopts. I'd like to see randomized pets, so not everyone is getting the exact same pets every single month and slowly building up a mass of pets that won't be traded or dressed up or anything. I feel like it would create a much higher interest in trading, it'd help with all of these pets that nobody is really doing anything with despite their rarity label. Or even user created adopts (actual pets, not user created lines), like Wajas or Flight Rising. The ability to create and make your own would be awesome, even if it's a lower rarity, it would create so much interest in trading these low rarity pets.