I assume Aero III shares the same button as Aero II? A great idea. It would mean that WHM would have a "finisher" of some sort and it'd solve the one-button issue. It'd be hard to implement as it would force the devs to create an AoE Dia down the line. Not that there's anything wrong with that. I'm sure, and I hope, they can do it at a later expansion (hopefully 8.0).
I'd also like to see WHM have something akin to SCH's Quicken Aetherflow from pre-Shb. Something that would lower the CD of PoM after the use of a certain spell or proc since it's now going to be integral to WHM's burst. This may not be possible to implement right now due to the existence of the two minute meta, but it would help if (knock on wood) PoM CD is still 120sec going into DT.