I’m curious how the devs ensvisage the cosmetic pet is going to help. I think I may be missing some key element, because otherwise…
Seems to me, most cosmetic pets are only available once (so far), and there hasn’t been any plan to repeat them (so far). I suspect the vast majority of people end up with 1 to 3 copies of any cosmetic pet. In late-game, it starts to become affordable to spend enough Gems in the Pet Shop 
to get 6 or even 16 copies. Six copies will enable 11 stars, which is nice.
However, my experience has been that kingdoms only really get “pet blocked” at 13 stars (and eventually 17 stars) – 31 copies are required to get a pet to level 20. Being in late-game but not end-game, this has been out of reach for me, so far. (Hope I’m getting the maths right.)
This thread suggests the pet drop rate from pet baskets is 10%. So on average, we get 3 copies from a new Pet Event (1 from Reward 8, 1 from Reward baskets (90%), 1 from the special event calendar). Another 3 copies are possible from Tier III (175 Gems), and guaranteed from Tier IV (375 Gems). That’s to get a L10 cosmetic pet.
Getting that pet to L15 (16 copies) does nothing for Kingdom Power. To get to L20, we need 28 additional copies – guaranteed by buying Tier VII 18 times (1075+1800 = 2875 Gems), or based on naive drop rate averaging, 13 times Tier VII (2375 Gems).
I draw two conclusions:
- Only end-game players and those who spend significant money on Gems are going to be able to get cosmetic pets to level 20 (assuming the value proposition makes sense to them).
- As a result, very few players are going to benefit from the upcoming cosmetic pet, UNLESS cosmetic pets start to return.
My suggestion, then, is that at least some cosmetic pets should return annually.