By my calculations: land alone gives W-U-B-R colour distribution of 23-26-26-23

Edits:
2018/10/05: IN Semblance Anvil; OUT Beacon of Unrest
2018/10/05: IN Karn, Scion of Urza; OUT Daretti, Ingenious Iconoclast (uggggggh I hope that's the right move)
2018/10/05: IN Krark-Clan Ironworks; OUT Chief Engineer
2018/05/XX: IN Sai, Master Thopterist; OUT Mycosynth Lattice
2018/04/19: IN Scrap Trawler, OUT Silas Renn, Seeker Adept

Maybeboard:
Thirst for Knowledge (swapped out in favour of Nihil Spellbomb)
Blood Artist (swapped out in favour of Coalition Relic)
Scrap Mastery
Ethersworn Canonist
Time Sieve?
Tezzeret the Seeker?
Whirler Rogue?
Master Trinketeer?
Pia and Kiran Nalaar?

Old mana base:

1 Azorius Chancery
1 Boros Garrison
1 Dimir Aqueduct
1 Rakdos Carnarium

5 Island
5 Swamp
4 Mountain
3 Plains

1 Arcane Sanctum
1 Crumbling Necropolis
1 Mystic Monastery
1 Nomad Outpost

1 Ancient Den
1 Great Furnace
1 Seat of the Synod
1 Vault of Whispers
1 Darksteel Citadel

1 Command Tower
1 Exotic Orchard
1 Rupture Spire
1 Transguild Promenade

1 Buried Ruin
1 Inventors’ Fair
1 Temple of the False God