Speaking of using returning boomerang to get off the ledge, something I've been experimenting with a bit lately has been to, with a bomb in hand, drop off the ledge and throw the boomerang straight forward, and then get back to the ledge. After that, immediately ledgehop and then ibomb. This results in the bomb covering the ledge area, and the boomerang returning to you through the bottom of the stage, covering the area below you, while you're mostly invincible during all of this.
It's in no way perfect, but as a mix-up it might work from time to time.
It's in no way perfect, but as a mix-up it might work from time to time.