New fatties:

• Gruff Triplets (check if enough sac outlets)
• Dusk Mangler

Bitterthorn, Nissa's Animus
Nissa, Resurgent Animist
The One Ring
Mirror of Galadriel
Throne of Eldraine
The Irencrag
Ojer Kaslem, Deepest Growth
Archdruid's Charm
Surrak and Goreclaw (haste enabler)
Ghalta, Stampede Tyrant
Delighted Halfling
The Ring Goes South
Glimpse the Core + some of:

• Pit of Offerings (tapped, graveyard hate)
• Hidden Nursery (tapped, value)
• Sunken Citadel (synergy with Nykthos/Castle Garenbrig)
• Volatile Fault (bad Wasteland)

Not on MTGO:
Jamie McCrimmon

Possible swaps:
Guardian Project -> The One Ring (same MV, same purpose, + legendary)
Beast Within -> Archdruid's Charm (more flexible, finally a spot for the Charm)
Burgeoning -> The Irencrag (similar purpose, + legendary)
Rhonas the Indomitable -> Nissa, Resurgent Animist
Sylvan Library -> Mirror of Galadriel (similar purpose, good spot for this niche card, + legendary)

Potential cuts:
Nissa, Who Shakes the World
Finale of Devastation

Sol Ring / Mana Crypt replacements:
Delighted Halfling
Rampant Growth
Llanowar Elves
Glimpse the Core + a Cave

Mutate

Auspicious Starrix - Elk Beast - Mutate 5G -> 5 Permanents

Gemrazer - Beast - Mutate 1GG -> Destroy 3 Artifacts/Enchantments

Migratory Greathorn - Beast - Mutate 2G -> 3 basics

Sawtusk Demolisher - Beast - Mutate 3G -> 3 Beast Within

Souvenir Snatcher - Bird - Mutate 5U -> Steal 3 noncreature artifacts

Dreamtail Heron - Elemental Bird - Mutate 3U -> 3 Cards

Other

Ongoing investigation!

Possible additions:

Archfiend of Ifnir
Ertai, the Corrupted
Overcharged Amalgam
Teferi, Master of Time
Linvala, Shield of Sea Gate
Burning Rune Demon
Nezahal, Primal Tide
Phyrexian Tower
Reveillark
Street Wraith
Toxrill, the Corrosive
Nephalia Drownyard
Cephalid Coliseum

Organ Hoarder

Moon-Blessed Cleric

Oriq Loremage
Thought Courier
Jace's Archivist
Thousand-Year Elixir

Loyal Warhound
Knight of the White Orchid

Tithing Blade
Virtue of Knowledge

Additions:
Soldevi Adnate (mana dork)
Basal Thrull (mana dork)
Whisper, Blood Liturgist (sacc outlet, recursion)
Skyscanner (card draw)
Abyssal Gatekeeper (removal?)
Worn Powerstone
Apprentice Necromancer
Leaden Myr

Interestting list: https://tappedout.net/mtg-decks/shirei-peasant/

Svella:

• Highland Weald -> Highland Forest
• Beast Within? Temple of the False God? Rogue's Passage? Rhythm of the Wild?

Harald:

• Eyeblight Massacre -> Heritage Druid
• Elvish Guidance?
• Lightning Greaves?

Araumi:

• Swamp -> Malakir Rebirth
• Stitcher's Supplier? Millikin? Port of Karfell? Talisman of Dominance?
• Tribute Mage? Corpse Connoisseur? Notion Rain? Impaler Shrike?