Welll, that's why I posted, cuz you didnt mention the double jump. For the edge guard to work, there needs to be space between you and the bomb. If you just drop it and dair after it, it's right under you. It's like your dair has a slightly larger hit box, but still, good players would have the same options of getting around your method as the original Dair edgeguard since the bomb is so close to Link. You need the double jump so your opponent has no way to get above or to the side of you to get a gimp.
The only way to do it from your method would be to release the bomb as soon as you begin the jump so that by the time you make it to the height of the jump, the bomb is far enough below you to do the edge guard. That's a lot harder to time though, and you didn't mention that in your explanation. It's actually more practical in competetive play, but the double jump is much easier for people getting used to the edge guard to learn and understand, which is what were trying to do for the boards.