[Idea] Let players use additional summoner spells in game (but only 2 can be active at once)

Since increasing diversity and strategy is something Riot is trying to value, one idea is letting players switch to another summoner spell in the game. Only 2 spells can be active at once, so the actual in-game interface wouldn't change.

Players can switch one or both of their spells out for any of the inactive spells at anytime, but the cool down of the newly active spell starts immediately. So this way, players can't use 3+ summoner spells at once. Or perhaps players can choose 3 spells before the game so 1 is always inactive.

I think this idea would create great opportunities for strategizing. Examples:

• If I know I struggle with mana in the early game, I could start with Clarity and then in the mid/late game switch that out with something more valuable once I have my mana item
• Switching to Teleport or Revive spells in the late game could potentially turn a game around with a clutch backdoor play or revive being able to neutralize an opponent base attack
• If I'm a carry getting killed a lot because of CC abilities, I could switch out my heal/barrier/ignite for Cleanse.
• If one player is dominating for the other team, I could switch out one of my spells for Exhaust to help contain him/her in a team fight.

Thoughts?