I do like your suggestions, and think Sneak Attack could fit right in
4 Scavenging Ooze Ooze That Just Keeps Growing 2 Mana Cost in Green Creature Scavenging Ooze is an infuriating creature to fight, going from a simple 2/2 upon its entrance to suddenly being a massive threat as long as its controller has mana and anyone in the game has a graveyard full of creatures
This has much the same effect on how fun the set ismore decision-making and less expensive cards stuck in the hand, which means more interesting games
I dont know that it is the best of the Charms (I would give that title to Izzet Charm), but unlike Izzet Charm, where you overpay by one mana for any of two to three desirable effects, you more-or-less break even on each of Selesnya Charms charming possibilities
And then theres white, the color that consistently feels like it gets the short end of the stick in many key gameplay elements of Commander, and mana ramp is no exception
Each of them represents both a combination of colors and an aspect of Ravnican society