Rather than investigating edge size, shouldn't the MCC think about pushing the boundary rope back to the edge of the field?
This.
The guy on the committee even says "With the rise of Twenty20, and boundaries getting shorter, there are more sixes being hit."
Push the boundaries back, more chance of being caught on the boundary. Simples.
As a second point, shirtfront wickets with near enough guaranteed bounce for five days in a test match also disadvantages the bowler, but there are no rules about creating a "competitive wicket".
Finally, as we well know on here, just because a bat is larger, it doesn't mean it weighs more, and most of us aren't supremely capable of timing the ball such that we hit sixes. Limiting the depth of the bat really is the most insane approach.
It's all about conservation of momentum, and batmakers can press a piece of wood weighing 2lb 10oz a number of ways, depending on what they want to achieve. limiting the size doesn't change this.