Basic Land? So players can have as many of them as they like in their decks? But, presumably, you can't actually add copies to your deck that you didn't draft, like Snow-Covered Island and friends.

I like that Orzhov Guildgate and friends provide the precedent for printing lands like this at common. The manafixing available at common is only going to get more plentiful from now on. (Although it's a pity that the Orzhov Basilica cycle are considered too good.)

So I assume you are going for the definition " measured piece or parcel of land" with plot here? Seems weird that a dark cave (natural) would be "measured". Also "dark" implies black, "cave" as subterran also usually implies black, sometimes red.

The only cavernous lands that add white mana use specific story elements to justify them like the white-blue-black character Dromar or the presumably plains-filled desert region of Koilos.

I can get behind the idea of the most simple of ETBT dual lands being basic. The new land type is really putting a question mark behind the "most simple" here.

Lookie here:

http://www.mtgsalvation.com/forums/magic-fundamentals/the-rumor-mill/774977-cards-280-287-simple-tap-dual-lands

They decided to make taplands always available for standard. they are found outside the main expansion, within special planeswalker decks and deck builders kits.