CE is kinda useless now and great rescue for OOO will be new DLC.

Maybe suggestion about sprites will be too mainstream, but meh, my idea is special, DLC-only "Legendary Battle Sprite" as DLC reward.

But how it will work with tiers? Theres list:

Tier 1: Legendary Sprite + {Special} Evo Catalyst (can be used only on DLC pet)
Tier 2: Legendary Sprite [if not obtainted already in other tier] + {Special} Advanced Evo Catalyst (can be used only on DLC pet)
Tier 3: Legendary Sprite [if not obtainted already in other tier] + {Special} Ultimate Evo Catalyst (can be used only on DLC pet)

That legendary sprite perks could be special in some way like Movement Speed incrase [But medium is really max], if it was deleted on normal sprites (idk, huh)