While this does occasionally fail, and these cards are still considered mediocre by the community, this extensive playtesting sometimes results in finding a hidden gem of a card, and this is precisely what happened with Cyberse Witch
Across all the types of cards you'll want to include, there is a "meta-class" of cards that can guide you: Commander staples
The Pokmon card Lucario 80/113 of Legendary Treasures also exists in Reverse version
What I especially like about Rampaging Yao Guai is its Enter The Battlefield ability, which triggers as soon as he's played - it destroys any number of target artifacts and/or enchantments with total mana value X or less
Once you add those into the mix, Mabel, Heir to Cragflame becomes a bomb rare that perfectly synergizes with what mice are trying to do
Gev, Scaled Scorch Magic's best lizard, Gev, Scaled Scorch puts a good foot forward as a nasty little aggro commander