I thought about making a cycle of cards, one for each color, that can be played as either a spell or a land. The cards would be split cards, like the Apocalypse spells. To avoid confusion i think that the spell half should be limited to instants or sorceries, so that if the card is in play it is obviously a land, which would eliminate some confusion.
These cards would have to be limited in some way: the land half would have to have some drawback and the spell half would have to be no better than any spell printed. I think the drawback for the land should be either CIPT or function as a pain land.
Here are my initial creations:
Red Land name // Red Spell name
Add

to your mana pool and ~this~ deals one damage to you. // 1

Sorcery: ~This~ deals 2 damage divided as you choose among any number of target creatures and/or players
Black Land name // Black Spell name
Add

to your mana pool and ~this~ deals one damage to you. // 2

Instant: Destroy target nonartifact, nonblack creature.
White Land name // White Spell name
Add

to your mana pool and ~this~ deals one damage to you. // 2

Instant: Remove target attacking creature from the game.
Blue Land name // Blue Spell name
Add

to your mana pool and ~this~ deals one damage to you. //

Instant: Return target non-land permanent to its owners hand.
Green Land name // Green Spell name
Add

to your mana pool and ~this~ deals one damage to you. // 1{G}{G} Sorcery: Put a 3/3 green Elephant token into play.
None of the effects are overpowering and thats how I want it. Compare to Fire, Terror, Devouring Light, Boomerang, and Pulse of the Tangle. All of these spells are slightly worse than their predecessor, but have the ability to be a land if you are mana starved.
Current Wording:
Red Land name // Red Spell name
Add
to your mana pool and ~this~ deals one damage to you. // 1
Sorcery: ~This~ deals 2 damage divided as you choose among any number of target creatures and/or players
Black Land name // Black Spell name
Add
to your mana pool and ~this~ deals one damage to you. // 2
Instant: Destroy target nonartifact, nonblack creature.
White Land name // White Spell name
Add
to your mana pool and ~this~ deals one damage to you. // 2
Instant: Remove target attacking creature from the game.
Blue Land name // Blue Spell name
Add
to your mana pool and ~this~ deals one damage to you. //
Instant: Return target non-land permanent to its owners hand.
Green Land name // Green Spell name
Add
to your mana pool and ~this~ deals one damage to you. // 1{G}{G} Sorcery: Put a 3/3 green Elephant token into play.