I'll leave the fine-tuning of %s to y'all. This is just the idea.
Legendary Enchant - Draft Only? Disabled or HEAVILY nerfed in PVP mode for sure.
Zookeeper
Removes all restrictions on Summoned/Tamed creature limits, allowing you to use any Skills/Spells that summon units to your aid. Also lowers Player damage output by a large enough % to encourage heavy reliance on Pet Usage.
Option 1: Makes all Summons permanent, instead of Timed, allowing you to have, for example: A Summoned Imp, 3 Treants, an Infernal, and a Water Elemental. Hand of Gul'dan would only spawn/respawn a maximum of 3 Wild Imps, not add more every cast, or change the spell to summon 3 wild imps while this enchant is on.
Option 2: Turns ALL pets into temporary ones, and normalizes all summon durations to 30 or 60 seconds, encouraging a "rotation" of summoning different pets, e.g; Hunter Pet, then Infernal, then Treants, then Feral Spirits, then Felhunter, etc. Obviously this would require the Enchant to change all pets into instant-cast summon spells instead of casts like the Felhunter. Similar to FFXIV's modern Summoner, but more pet-focused than pet-themed.