Okay, so the creatures that assign damage based on your creatures' toughness that are in the Maybeboard are a good start.

I'm of the firm belief every deck should have at least one Alternate Win Card. May I suggest any combination of Angel of Destiny and Triskaidekaphobia? With the latter you can add in Tree of Perdition for a win combo.

Speaking of trees have you considered Tree of Redemption? If you add that with Huatli, the Sun's Heart you have a life gain boost if you can find a way to blink her.

Honestly, Unless you plan to add any combination of Inversion Behemoth and Transmutation to your deck, I don't see the point of having cards such as Loathsome Troll and Yargle.

Finally, I would recommend Crenellated Wall, Crystal Barricade, Felothar the Steadfast and Sidar Kondo of Jamuraa. Though in the case of the last one you'll have to reconsider some of the deck as you'll need creatures with power 2 or less.

I hope these help. Thank you for reading me out. Happy Hunting!

Hey, Reuben_Medik! Will you please provide a Maybeboard of cards in your list to acquire so we know what you wish to work with? Thank you in advance!

Mat'Selesnya, Parun of Selesnya

Legendary Creature- Avatar Elemental

Reach, Vigilance

~ enters with X +1/+1 counters on it equal to the number of creatures tapped to cast it.

Whenever a spell with convoke is cast, Populate.

0/0

Create a Commander that allows you to search and/or wish for any combination of Background, Companion(Doctor Who and Ikoria apply), Friends Forever, and Partner.

No challenge, so I'm going for it.

Thrice More Upon The Breach

Legendary Enchantment

Flash

End the Turn

Creatures you control have +2/+0, Double Strike, Flying and Lifelink.

Target Opponent gets two extra turns. The turns cannot be skipped and spells and abilities cannot cause the turns to end early. When the opponent's third consecutive turn ends, they lose the game.

Wild

With monogreen I'm thinking permanents that do additional land plays including, but not limited to, Arboreal Grazer, Azusa, Lost but Seeking, Oracle of Mul Daya and Walking Atlas. Another for your deck would be Courser of Kruphix. I hope this helps. Happy Hunting!

Zaid's Herd

Legendary Creature- Aurochs

Trample

Whenever ~ attacks, it gets +1+0 for each other attacking Aurochs. If it's saddled, it gets +3/+1 for each attacking Aurochs and vigilance instead.

Saddle 2

4/3

Create a monowhite Aurochs that gives other Aurochs Saddle X.