Chiming in! My list is a fairly straightforward 630, and this set is pretty insane. I've added 28 cards and am considering adding a couple more.
White:
Luminarch Aspirant: Card seems great both in and out of aggro. It has a virtual point of haste by putting a counter elsewhere the turn it comes down, and scales really well over time. Cut
Leonin Relic-Warder for it, since Relic-Warder was a lower-tier combo piece.
Skyclave Apparition: Being a hybrid between
Oblivion Ring and
Baffling End on a 2/2 feels like a solid 3-drop. I'm not sure how long this will stick around, but it's got nice flexibility. Cut
Thalia, Heretic Cathar, who I love, but was the most eminently cuttable 3-drop in white.
Emeria's Call // Emeria, Shattered Skyclave: I'm adding a
lot of MDFCs from this set. This, along with the rest of the mythic cycle, are being classified as lands, since that's what they'll often be, but the flexibility is amazing. Cut
Winds of Abandon for this. Winds is a fine removal spell, but I preferred cutting it to
Serra the Benevolent, which was the other consideration.
Blue:
Sea Gate Stormcaller: This isn't winning any prizes in the 2-drop department for blue, but I like the idea of how it plays, and it's one a few creatures in this set that's helping increase creature density in blue for me (I've cut lower-performing spells instead of other creatures). Cut for this one is
Spell Pierce.
Thieving Skydiver: This will probably not perform
as well in an unpowered setting as a powered one, but it still seems like a solid addition that'll stick around for a while. Cut
Ghostly Pilferer, which was sadly only in for one set and didn't even get physically drafted thanks to the pandemic.
Glasspool Mimic // Glasspool Shore: This card was sort of an on-the-fence one, but I was convinced to take it for a spin. Only cloning your own creatures is a bit rough, but the flexibility with the land side is still great. I cut
Gifts Ungiven to make room for this one.
Jace, Mirror Mage: Seems like a pretty straightforward swap for
Jace Beleren for me, sadly enough. This means that only one OG Lorwyn walker is left in the cube (unsurprisingly, it's
Garruk Wildspeaker).
Jwari Disruption // Jwari Ruins: I like MDFCs a lot more than the same card with cycling, so I'm trying this even though I only briefly tried
Censor. I cut
Ancestral Vision for this, which is a good removal spell that's a bit slow without good access to cascade or similar effects.
Sea Gate Restoration // Sea Gate, Reborn: Easily the least compelling of the mythic MDFCs, but still worth a slot to me. I cut
Thirst for Knowledge to make room for this.
Black:
Nullpriest of Oblivion: A pretty nuts aggro card that has some late-game flexibility. Putting menace on a
Child of Night is pretty big game even if you don't kick it. I axed
Nezumi Graverobber // Nighteyes the Desecrator for this. Sorry little rat friend.
Skyclave Shade: Recurrable 2-drops are great for black aggro, and this can even come back bigger! Seems like an easy include, and the showcase art on this one is
outstanding. I cut
Night Incarnate here to go +1 on aggro 2-drops for the cube.
Nighthawk Scavenger: A virtually strictly better
Vampire Nighthawk. Assuming that
anything ends up in your opponent's graveyard, you're already at the same level, and it has the opportunity to scale nicely. The cut here is straightforward - I still ran
Vampire Nighthawk and don't need both.
Hagra Mauling // Hagra Broodpit: This was the non-mythic MDFC I was most on the fence about, but want to try out. 4 mana feels like a lot for removal, but am still erring on the side of the flexibility being very strong. I cut
The Eldest Reborn for it.
Agadeem's Awakening // Agadeem, the Undercrypt: This might be the mythic MDFC I'm most interested in seeing in action. The scaling seems really awesome for a black midrange deck later on. I cut
Profane Command for this, which hurt. The swap seemed most comparable, though.
Red:
Kargan Intimidator: A solid if not amazing 2-drop. It's definitely good enough to make it in the cube, though, so it's replacing
Abbot of Keral Keep.
Roil Eruption: A very strong
Volcanic Hammer variant. The kicker cost is expensive, but I think it's enough to get the nod. I'm axing
Magma Jet to make room.
Shatterskull Smashing // Shatterskull, the Hammer Pass: Easily the best MDFC in my opinion, since it's so flexible as a spell in addition to being a land. This replaces
Flames of the Firebrand.
Green:
Tangled Florahedron // Tangled Vale: A fairly unassuming MDFC, but the land/mana dork flexibility seems nice and clean. I'm cutting
Mayor of Avabruck // Howlpack Alpha, which recently came into the cube but doesn't have a lot of Humans support.
Kazandu Mammoth // Kazandu Valley: This card seems playable even without the land side, but the flexibility pushes it over the top. I was looking for a 3-drop beater to replace
Manglehorn, and found it here.
Bala Ged Recovery // Bala Ged Sanctuary: A very cool
Regrowth variant that's playable early as a land when you won't be able to leverage the regrowth effect yet. Kicks
Den Protector out of the cube, since 4 of this effect seems like a lot (the other two being Regrowth and
Eternal Witness).
Turntimber Symbiosis // Turntimber, Serpentine Wood: Definitely a neat effect for an MDFC, and easily makes the list. Finding a cut for this one was tougher, but ultimately I decided to axe
Oath of Nissa. I'm still mulling this one over, though.
Multicolor:
Overall, I'm playing all of the Pathway lands. Despite locking yourself into a color, they always enter untapped, which can be a huge difference. Here are the land cuts by guild.
Clearwater Pathway // Murkwater Pathway: Cutting
Temple of Deceit.
Cragcrown Pathway // Timbercrown Pathway: Cutting
Cinder Glade.
Branchloft Pathway // Boulderloft Pathway: Cutting
Canopy Vista.
Brightclimb Pathway // Grimclimb Pathway: Cutting
Concealed Courtyard.
Riverglide Pathway // Lavaglide Pathway: Cutting
Spirebluff Canal.
Needleverge Pathway // Pillarverge Pathway: Cutting
Inspiring Vantage.
Colorless:
I'm not adding
Skyclave Relic yet, but I'm still considering it. Can't find a cut I like enough, although the kicked effect is compelling for artifact-matters things.