In Commander, mana dorks are run in the majority of green decks, so this seems like an easy ramp staple
You play a lot of lands that enter the battlefield tapped, but as a two color deck containing green, Im not sure if you need to
Im not sure what legend you might be able to use to actually take advantage of it (maybe Iname as One or Jugan, the Rising Star?), but its something to ponder Everybody Accelerate Collective Voyage, Eladamris Vineyard, Magus of the Vineyard, New Frontiers, Veteran Explorer, Clear the Path, Rites of Flourishing
Besides, the lack of balance means this deck would never cut it against custom creations
Whenever a Vampire you control deals combat damage to a player, put a +1/+1 counter on it
Ghalta, Stampede Tyrant does that with the right combination of ETBs in hand, although I cant quite put my finger on the right combo