To whom it may concern,
Currently on Arena, some modern decks are craftable and playable, with the option to test them in challenges against friends. Others are missing a card or two, sometimes cards that are in the arena but just aren't allowed to be collected.

This message is an attempt to have those cards added/get an update on when they will be added, as it is incredibly helpful for testing the format. Below is the list of cards I am inquiring about. Thank you for your assistance!

Cards that are on Arena but not able to be collected:

Urza's Saga
Urza's Mine
Urza's Power Plant
Urza's Tower
Cards that are not on Arena (would like them to be added):

Obsidian Charmaw
Celestial Purge
Desperate Ritual
Pyretic Ritual
Scion of Draco
Dryad Arbor
Summoner's Pact
Amulet of Vigor
Gruul Turf
Simic Growth Chamber
Tolaria West
Vesuva
Allosaurus Rider
Nourishing Shoal
Shardless Agent
Street Wraith
Living End
Flooded Grove
Murktide Regent
Lava Dart
Mutagenic Growth
Disrupting Shoal
Lotus Bloom
Goryo's Vengeance
Cards for Sideboards

Ensnaring Bridge
Trinisphere
Walking Ballista
Claws of Gix
Engineered Explosives
Whipflare
Collector Ouphe
Firespout
Inevitable Betrayal
Foundation Breaker
Hurkyl's Recall
Tezzeret the Seeker
In total its making 4 cards collectable on arena, 24 cards to make the top 15 decks in modern playable with their 60 mainboard cards and then an additional 12 cards to make their sideboards fully playable as well.