Shroud/Indestructible multi-colored lands. Conditional draw. Making things uncounterable. Producing 3 or more, or filtering for double color. These are effects sometimes worth playing over duals. If they pushed those mechanics far enough, they could be playable over the traditional set up.
For what it's worth, any land with Shroud/Hexproof/Indestructable that produced colored mana could potentially be huge. I mean if you had:
This land is Indestructible. When this land comes into play take one damage.
People would absolutely run this over at least one basic island just to protect from decks that recur stripmine. I also think this design is far more likely to happen than a dual with the same stuff printed on it. The issue is without the island subtype the card is very likely not good enough if not just actively bad, but if you put the island subtype on it suddenly it is fetchable and fetches remain king.